Dermatopathology

The Diagnosis: Interstitial Granulomatous Dermatitis 

Interstitial granulomatous dermatitis (IGD) is rare, and the exact incidence is unknown, with only a few cases reported in the literature annually.¹ Although IGD may arise in both children and adults, it occurs more commonly in adults, with an age of onset of 52 to 58.5 years. Interstitial granulomatous dermatitis also shows a female predominance.¹  

Interstitial granulomatous dermatitis may present as annular flesh-colored or erythematous to violaceous papules and plaques, or less commonly erythematous linear cordlike subcutaneous nodules (called the rope sign).¹ Lesions often are asymptomatic but may be pruritic or tender. Interstitial granulomatous dermatitis has been associated with autoimmune conditions such as rheumatoid arthritis, systemic lupus erythematosus, and primary biliary cholangitis, and rarely malignancy.² Interstitial granulomatous drug reactions can occur months to years after initiation of therapy with offending agents, and common causes include calcium channel blockers, statins, and tumor necrosis factor α inhibitors.³  

Interstitial granulomatous dermatitis and palisaded neutrophilic and granulomatous dermatitis (PNGD) demonstrate overlapping clinical features and are thought to be part of the same spectrum of granulomatous dermatitis.⁴ Both IGD and PNGD may present with symmetric flesh-colored to erythematous papules or erythematous annular or linear plaques.⁵ Interstitial granulomatous dermatitis and PNGD may be differentiated through histopathologic examination.  

Histopathology of IGD shows an interstitial infiltrate of epithelioid histiocytes in the dermis, often surrounding foci of degenerated collagen resembling palisading granulomas (quiz images).¹ Perivascular and interstitial lymphocytic infiltrates also are present in most cases. Epidermal changes are minimal in IGD but can be associated with interstitial granulomatous drug reactions.¹ There usually is no vasculitis, and mucin typically is absent, unlike granuloma annulare (GA).^3,6 In comparison, histopathologic examination of PNGD shows basophilic degenerated collagen surrounded by palisades of histiocytes, neutrophils, and nuclear debris with focal areas of leukocytoclastic vasculitis and rare mucin.⁵  

No specific treatment is recommended, and lesions may resolve without any therapy. Reported treatments include topical, intralesional, or systemic steroids; nonsteroidal anti-inflammatory drugs; methotrexate; hydroxychloroquine; and cyclosporine.⁶ Due to the strong association with systemic diseases, it is important to evaluate patients with IGD for autoimmune diseases and conduct age-appropriate cancer screening. Furthermore, a review of medications is warranted to assess the possibility of interstitial granulomatous drug reactions.⁶ In our patient, rheumatologic workup and age-appropriate cancer screenings were negative, and the rash spontaneously resolved without treatment. 

Granuloma annulare presents with asymptomatic flesh-colored to erythematous papules and plaques in an annular configuration. In the localized variant of GA, plaques frequently localize to the distal extremities, especially the dorsal hands, as in our patient. Other variants include generalized GA, subcutaneous GA, and perforating GA. Mucin and a palisading or interstitial pattern of granulomatous inflammation are key features on histopathology in all subtypes of GA (Figure 1).⁷ Patch GA is a rare variant that presents with asymptomatic erythematous to brown patches, is associated with interstitial-type inflammation on histopathology, and can be difficult to distinguish from IGD.⁸ Granuloma annulare with interstitial inflammation on histology can be differentiated from IGD by the comparative lack of mucin in IGD.⁷ 

Sweet syndrome (SS) is characterized by sudden-onset, painful, erythematous plaques and/or nodules, commonly associated with fever and leukocytosis. Clinical variants of SS include pustular and bullous SS; giant cellulitis-like SS; necrotizing SS; and neutrophilic dermatosis of the dorsal hands presenting with hemorrhagic bullae, plaques, and pustules.^7-9 Histopathologic examination shows dense nodular or perivascular neutrophilic infiltrate in the dermis without evidence of vasculitis (Figure 2).¹⁰ Histopathologic variants include histiocytoid, lymphocytic, subcutaneous, and cryptococcoid.⁹ The classic variant of SS has a bandlike, predominantly neutrophilic infiltrate with marked leukocytoclasia, which can be differentiated from the histiocytoid infiltrate of IGD.¹¹ It has been shown that the infiltrate of the histiocytoid variant of SS is composed of myeloperoxidase-positive, immature myeloid cells rather than true histiocytes, and therefore can be differentiated from IGD.¹² Lastly, all variants of SS have dermal edema, which typically is absent in IGD, and SS has no evidence of necrobiosis.  

Erythema elevatum diutinum (EED) is a rare disease that presents with bilateral violaceous or erythematous to brown papules, plaques, or nodules. Lesions frequently localize to extensor surfaces, including the hands and fingers, and may be asymptomatic or associated with pruritus, burning, or tingling.¹³ Early EED lesions are characterized by leukocytoclastic vasculitis of the papillary and mid-dermal vessels with a perivascular neutrophilic infiltrate and perivascular fibrinoid necrosis. With older EED lesions, dermal and perivascular onion skin-like fibrosis become more prominent (Figure 3).¹⁴ The neutrophilic infiltrate, dermal fibrosis, and chronic vasculitic changes distinguish EED from IGD. 

Necrobiosis lipoidica (NL) is a rare disease that presents with well-demarcated, yellow to red-brown papules and nodules most commonly localized to the bilateral lower extremities on the pretibial area. Papules and nodules evolve into plaques over time, and ulceration is common.¹⁵ On histopathology, NL primarily exhibits granulomatous inflammation with parallel palisading (Figure 4). The hallmark feature is necrobiosis--or degeneration--of collagen; the alternation of necrobiotic collagen and inflammatory infiltrate creates a layered cake-like appearance on low power.¹⁶ The clinical presentation as well as the dermal necrobiotic granuloma consisting of a large confluent area of necrobiosis centered in the superficial dermis and subcutaneous tissue of NL distinguishes it from the histiocytic infiltrate of IGD.  

The Diagnosis: Interstitial Granulomatous Dermatitis 

Interstitial granulomatous dermatitis (IGD) is rare, and the exact incidence is unknown, with only a few cases reported in the literature annually.¹ Although IGD may arise in both children and adults, it occurs more commonly in adults, with an age of onset of 52 to 58.5 years. Interstitial granulomatous dermatitis also shows a female predominance.¹  

Interstitial granulomatous dermatitis may present as annular flesh-colored or erythematous to violaceous papules and plaques, or less commonly erythematous linear cordlike subcutaneous nodules (called the rope sign).¹ Lesions often are asymptomatic but may be pruritic or tender. Interstitial granulomatous dermatitis has been associated with autoimmune conditions such as rheumatoid arthritis, systemic lupus erythematosus, and primary biliary cholangitis, and rarely malignancy.² Interstitial granulomatous drug reactions can occur months to years after initiation of therapy with offending agents, and common causes include calcium channel blockers, statins, and tumor necrosis factor α inhibitors.³  

Interstitial granulomatous dermatitis and palisaded neutrophilic and granulomatous dermatitis (PNGD) demonstrate overlapping clinical features and are thought to be part of the same spectrum of granulomatous dermatitis.⁴ Both IGD and PNGD may present with symmetric flesh-colored to erythematous papules or erythematous annular or linear plaques.⁵ Interstitial granulomatous dermatitis and PNGD may be differentiated through histopathologic examination.  

Histopathology of IGD shows an interstitial infiltrate of epithelioid histiocytes in the dermis, often surrounding foci of degenerated collagen resembling palisading granulomas (quiz images).¹ Perivascular and interstitial lymphocytic infiltrates also are present in most cases. Epidermal changes are minimal in IGD but can be associated with interstitial granulomatous drug reactions.¹ There usually is no vasculitis, and mucin typically is absent, unlike granuloma annulare (GA).^3,6 In comparison, histopathologic examination of PNGD shows basophilic degenerated collagen surrounded by palisades of histiocytes, neutrophils, and nuclear debris with focal areas of leukocytoclastic vasculitis and rare mucin.⁵  

No specific treatment is recommended, and lesions may resolve without any therapy. Reported treatments include topical, intralesional, or systemic steroids; nonsteroidal anti-inflammatory drugs; methotrexate; hydroxychloroquine; and cyclosporine.⁶ Due to the strong association with systemic diseases, it is important to evaluate patients with IGD for autoimmune diseases and conduct age-appropriate cancer screening. Furthermore, a review of medications is warranted to assess the possibility of interstitial granulomatous drug reactions.⁶ In our patient, rheumatologic workup and age-appropriate cancer screenings were negative, and the rash spontaneously resolved without treatment. 

Granuloma annulare presents with asymptomatic flesh-colored to erythematous papules and plaques in an annular configuration. In the localized variant of GA, plaques frequently localize to the distal extremities, especially the dorsal hands, as in our patient. Other variants include generalized GA, subcutaneous GA, and perforating GA. Mucin and a palisading or interstitial pattern of granulomatous inflammation are key features on histopathology in all subtypes of GA (Figure 1).⁷ Patch GA is a rare variant that presents with asymptomatic erythematous to brown patches, is associated with interstitial-type inflammation on histopathology, and can be difficult to distinguish from IGD.⁸ Granuloma annulare with interstitial inflammation on histology can be differentiated from IGD by the comparative lack of mucin in IGD.⁷ 

Sweet syndrome (SS) is characterized by sudden-onset, painful, erythematous plaques and/or nodules, commonly associated with fever and leukocytosis. Clinical variants of SS include pustular and bullous SS; giant cellulitis-like SS; necrotizing SS; and neutrophilic dermatosis of the dorsal hands presenting with hemorrhagic bullae, plaques, and pustules.^7-9 Histopathologic examination shows dense nodular or perivascular neutrophilic infiltrate in the dermis without evidence of vasculitis (Figure 2).¹⁰ Histopathologic variants include histiocytoid, lymphocytic, subcutaneous, and cryptococcoid.⁹ The classic variant of SS has a bandlike, predominantly neutrophilic infiltrate with marked leukocytoclasia, which can be differentiated from the histiocytoid infiltrate of IGD.¹¹ It has been shown that the infiltrate of the histiocytoid variant of SS is composed of myeloperoxidase-positive, immature myeloid cells rather than true histiocytes, and therefore can be differentiated from IGD.¹² Lastly, all variants of SS have dermal edema, which typically is absent in IGD, and SS has no evidence of necrobiosis.  

Erythema elevatum diutinum (EED) is a rare disease that presents with bilateral violaceous or erythematous to brown papules, plaques, or nodules. Lesions frequently localize to extensor surfaces, including the hands and fingers, and may be asymptomatic or associated with pruritus, burning, or tingling.¹³ Early EED lesions are characterized by leukocytoclastic vasculitis of the papillary and mid-dermal vessels with a perivascular neutrophilic infiltrate and perivascular fibrinoid necrosis. With older EED lesions, dermal and perivascular onion skin-like fibrosis become more prominent (Figure 3).¹⁴ The neutrophilic infiltrate, dermal fibrosis, and chronic vasculitic changes distinguish EED from IGD. 

Necrobiosis lipoidica (NL) is a rare disease that presents with well-demarcated, yellow to red-brown papules and nodules most commonly localized to the bilateral lower extremities on the pretibial area. Papules and nodules evolve into plaques over time, and ulceration is common.¹⁵ On histopathology, NL primarily exhibits granulomatous inflammation with parallel palisading (Figure 4). The hallmark feature is necrobiosis--or degeneration--of collagen; the alternation of necrobiotic collagen and inflammatory infiltrate creates a layered cake-like appearance on low power.¹⁶ The clinical presentation as well as the dermal necrobiotic granuloma consisting of a large confluent area of necrobiosis centered in the superficial dermis and subcutaneous tissue of NL distinguishes it from the histiocytic infiltrate of IGD.  

The Diagnosis: Interstitial Granulomatous Dermatitis 

Interstitial granulomatous dermatitis (IGD) is rare, and the exact incidence is unknown, with only a few cases reported in the literature annually.¹ Although IGD may arise in both children and adults, it occurs more commonly in adults, with an age of onset of 52 to 58.5 years. Interstitial granulomatous dermatitis also shows a female predominance.¹  

Interstitial granulomatous dermatitis may present as annular flesh-colored or erythematous to violaceous papules and plaques, or less commonly erythematous linear cordlike subcutaneous nodules (called the rope sign).¹ Lesions often are asymptomatic but may be pruritic or tender. Interstitial granulomatous dermatitis has been associated with autoimmune conditions such as rheumatoid arthritis, systemic lupus erythematosus, and primary biliary cholangitis, and rarely malignancy.² Interstitial granulomatous drug reactions can occur months to years after initiation of therapy with offending agents, and common causes include calcium channel blockers, statins, and tumor necrosis factor α inhibitors.³  

Interstitial granulomatous dermatitis and palisaded neutrophilic and granulomatous dermatitis (PNGD) demonstrate overlapping clinical features and are thought to be part of the same spectrum of granulomatous dermatitis.⁴ Both IGD and PNGD may present with symmetric flesh-colored to erythematous papules or erythematous annular or linear plaques.⁵ Interstitial granulomatous dermatitis and PNGD may be differentiated through histopathologic examination.  

Histopathology of IGD shows an interstitial infiltrate of epithelioid histiocytes in the dermis, often surrounding foci of degenerated collagen resembling palisading granulomas (quiz images).¹ Perivascular and interstitial lymphocytic infiltrates also are present in most cases. Epidermal changes are minimal in IGD but can be associated with interstitial granulomatous drug reactions.¹ There usually is no vasculitis, and mucin typically is absent, unlike granuloma annulare (GA).^3,6 In comparison, histopathologic examination of PNGD shows basophilic degenerated collagen surrounded by palisades of histiocytes, neutrophils, and nuclear debris with focal areas of leukocytoclastic vasculitis and rare mucin.⁵  

No specific treatment is recommended, and lesions may resolve without any therapy. Reported treatments include topical, intralesional, or systemic steroids; nonsteroidal anti-inflammatory drugs; methotrexate; hydroxychloroquine; and cyclosporine.⁶ Due to the strong association with systemic diseases, it is important to evaluate patients with IGD for autoimmune diseases and conduct age-appropriate cancer screening. Furthermore, a review of medications is warranted to assess the possibility of interstitial granulomatous drug reactions.⁶ In our patient, rheumatologic workup and age-appropriate cancer screenings were negative, and the rash spontaneously resolved without treatment. 

Granuloma annulare presents with asymptomatic flesh-colored to erythematous papules and plaques in an annular configuration. In the localized variant of GA, plaques frequently localize to the distal extremities, especially the dorsal hands, as in our patient. Other variants include generalized GA, subcutaneous GA, and perforating GA. Mucin and a palisading or interstitial pattern of granulomatous inflammation are key features on histopathology in all subtypes of GA (Figure 1).⁷ Patch GA is a rare variant that presents with asymptomatic erythematous to brown patches, is associated with interstitial-type inflammation on histopathology, and can be difficult to distinguish from IGD.⁸ Granuloma annulare with interstitial inflammation on histology can be differentiated from IGD by the comparative lack of mucin in IGD.⁷ 

Sweet syndrome (SS) is characterized by sudden-onset, painful, erythematous plaques and/or nodules, commonly associated with fever and leukocytosis. Clinical variants of SS include pustular and bullous SS; giant cellulitis-like SS; necrotizing SS; and neutrophilic dermatosis of the dorsal hands presenting with hemorrhagic bullae, plaques, and pustules.^7-9 Histopathologic examination shows dense nodular or perivascular neutrophilic infiltrate in the dermis without evidence of vasculitis (Figure 2).¹⁰ Histopathologic variants include histiocytoid, lymphocytic, subcutaneous, and cryptococcoid.⁹ The classic variant of SS has a bandlike, predominantly neutrophilic infiltrate with marked leukocytoclasia, which can be differentiated from the histiocytoid infiltrate of IGD.¹¹ It has been shown that the infiltrate of the histiocytoid variant of SS is composed of myeloperoxidase-positive, immature myeloid cells rather than true histiocytes, and therefore can be differentiated from IGD.¹² Lastly, all variants of SS have dermal edema, which typically is absent in IGD, and SS has no evidence of necrobiosis.  

Erythema elevatum diutinum (EED) is a rare disease that presents with bilateral violaceous or erythematous to brown papules, plaques, or nodules. Lesions frequently localize to extensor surfaces, including the hands and fingers, and may be asymptomatic or associated with pruritus, burning, or tingling.¹³ Early EED lesions are characterized by leukocytoclastic vasculitis of the papillary and mid-dermal vessels with a perivascular neutrophilic infiltrate and perivascular fibrinoid necrosis. With older EED lesions, dermal and perivascular onion skin-like fibrosis become more prominent (Figure 3).¹⁴ The neutrophilic infiltrate, dermal fibrosis, and chronic vasculitic changes distinguish EED from IGD. 

Necrobiosis lipoidica (NL) is a rare disease that presents with well-demarcated, yellow to red-brown papules and nodules most commonly localized to the bilateral lower extremities on the pretibial area. Papules and nodules evolve into plaques over time, and ulceration is common.¹⁵ On histopathology, NL primarily exhibits granulomatous inflammation with parallel palisading (Figure 4). The hallmark feature is necrobiosis--or degeneration--of collagen; the alternation of necrobiotic collagen and inflammatory infiltrate creates a layered cake-like appearance on low power.¹⁶ The clinical presentation as well as the dermal necrobiotic granuloma consisting of a large confluent area of necrobiosis centered in the superficial dermis and subcutaneous tissue of NL distinguishes it from the histiocytic infiltrate of IGD.  

Kaposi sarcoma (KS) is a low-grade vascular tumor that is rare among the general US population, with an incidence rate of less than 1 per 100,000.¹ The tumor is more common among certain groups of individuals due to geographic differences in the prevalence of KS-associated herpesvirus (also referred to as human herpesvirus 8) as well as host immune factors.² Kaposi sarcoma often is defined by the patient's predisposing characteristics yielding the following distinct epidemiologic subtypes: (1) classic KS is a rare disease affecting older men of Mediterranean descent; (2) African KS is an endemic cancer with male predominance in sub-Saharan Africa; (3) AIDS-associated KS is an often aggressive AIDS-defining illness; and (4) iatrogenic KS occurs in patients on immunosuppressive therapy.³ When evaluating a patient without any of these risk factors, the clinical suspicion for KS may be low. We report a patient with postpolio syndrome (PPS) who presented with KS of the right leg, ankle, and foot. 

A 77-year-old man with a distant history of paralytic poliomyelitis presented for an annual skin examination with concern for a new lesion on the right ankle. The patient had a history of PPS primarily affecting the right leg. Physical examination revealed residual weakness in an atrophic right lower extremity with a mottled appearance and mild pitting edema to the knee. Two red, dome-shaped, vascular papules were appreciated on the medial aspect of the right ankle (Figure 1), and a shave biopsy of the larger papule was performed. Microscopic examination of the biopsy specimen was consistent with KS (Figure 2). This patient had no history of human immunodeficiency virus or immunosuppressive therapy and was not of Mediterranean descent. 

Because KS is a radiosensitive vascular neoplasm and radiation therapy (RT) alone can achieve local control,⁴ the patient was treated with 6 megaelectron-volt electron-beam RT. He received 30 Gy in 10 fractions to the affected area of the medial ankle. The patient tolerated RT well. Three weeks after completing treatment, he was found to have mild lichenification on the right medial ankle with no clinical evidence of disease. Four months later, he presented with multiple additional vascular papules on the right third toe and in the interdigital web space (Figure 3). Shave biopsy of one of these lesions was consistent with KS. Contrast computed tomography of the chest, abdomen, and pelvis was performed, revealing no evidence of metastatic disease. The patient was treated with 30 Gy in 15 fractions using opposed lateral 6 megaelectron-volt photon fields to the entire right lower extremity below the knee to treat all of the skin affected by the PPS. His posttreatment course was complicated by edema in the affected leg that resolved after daily pneumatic compression. He had no evidence of residual or recurrent disease 6 months after completing RT (Figure 4). 

Cutaneous KS is a human herpesvirus 8-positive tumor of endothelial origin typically seen in older men of Mediterranean or African descent and among immunosuppressed patients.⁴ Our patient did not have any classic risk factors for KS, but his disease did arise in the setting of a right lower extremity that was notably affected by PPS. Postpolio syndrome is characterized by muscle atrophy due to denervation of the motor unit.⁵ Bruno et al⁶ found that such deficits in motor innervation could lead to impairments in venous outflow causing cutaneous venous congestion. Acroangiodermatitis clinically resembles KS but is a benign reactive vasoproliferative disorder and is well known to occur in the lower extremities as a sequela of chronic venous insufficiency.⁷ A case of bilateral lower extremity pseudo-KS was reported in a patient with notable PPS.⁸ A report of 2 patients describes KS arising in the setting of chronic venous insufficiency without any classic risk factors.⁹ Therefore, patients with PPS characterized by venous insufficiency may represent a population at increased risk for KS. 
 

Kaposi sarcoma (KS) is a low-grade vascular tumor that is rare among the general US population, with an incidence rate of less than 1 per 100,000.¹ The tumor is more common among certain groups of individuals due to geographic differences in the prevalence of KS-associated herpesvirus (also referred to as human herpesvirus 8) as well as host immune factors.² Kaposi sarcoma often is defined by the patient's predisposing characteristics yielding the following distinct epidemiologic subtypes: (1) classic KS is a rare disease affecting older men of Mediterranean descent; (2) African KS is an endemic cancer with male predominance in sub-Saharan Africa; (3) AIDS-associated KS is an often aggressive AIDS-defining illness; and (4) iatrogenic KS occurs in patients on immunosuppressive therapy.³ When evaluating a patient without any of these risk factors, the clinical suspicion for KS may be low. We report a patient with postpolio syndrome (PPS) who presented with KS of the right leg, ankle, and foot. 

A 77-year-old man with a distant history of paralytic poliomyelitis presented for an annual skin examination with concern for a new lesion on the right ankle. The patient had a history of PPS primarily affecting the right leg. Physical examination revealed residual weakness in an atrophic right lower extremity with a mottled appearance and mild pitting edema to the knee. Two red, dome-shaped, vascular papules were appreciated on the medial aspect of the right ankle (Figure 1), and a shave biopsy of the larger papule was performed. Microscopic examination of the biopsy specimen was consistent with KS (Figure 2). This patient had no history of human immunodeficiency virus or immunosuppressive therapy and was not of Mediterranean descent. 

Because KS is a radiosensitive vascular neoplasm and radiation therapy (RT) alone can achieve local control,⁴ the patient was treated with 6 megaelectron-volt electron-beam RT. He received 30 Gy in 10 fractions to the affected area of the medial ankle. The patient tolerated RT well. Three weeks after completing treatment, he was found to have mild lichenification on the right medial ankle with no clinical evidence of disease. Four months later, he presented with multiple additional vascular papules on the right third toe and in the interdigital web space (Figure 3). Shave biopsy of one of these lesions was consistent with KS. Contrast computed tomography of the chest, abdomen, and pelvis was performed, revealing no evidence of metastatic disease. The patient was treated with 30 Gy in 15 fractions using opposed lateral 6 megaelectron-volt photon fields to the entire right lower extremity below the knee to treat all of the skin affected by the PPS. His posttreatment course was complicated by edema in the affected leg that resolved after daily pneumatic compression. He had no evidence of residual or recurrent disease 6 months after completing RT (Figure 4). 

Cutaneous KS is a human herpesvirus 8-positive tumor of endothelial origin typically seen in older men of Mediterranean or African descent and among immunosuppressed patients.⁴ Our patient did not have any classic risk factors for KS, but his disease did arise in the setting of a right lower extremity that was notably affected by PPS. Postpolio syndrome is characterized by muscle atrophy due to denervation of the motor unit.⁵ Bruno et al⁶ found that such deficits in motor innervation could lead to impairments in venous outflow causing cutaneous venous congestion. Acroangiodermatitis clinically resembles KS but is a benign reactive vasoproliferative disorder and is well known to occur in the lower extremities as a sequela of chronic venous insufficiency.⁷ A case of bilateral lower extremity pseudo-KS was reported in a patient with notable PPS.⁸ A report of 2 patients describes KS arising in the setting of chronic venous insufficiency without any classic risk factors.⁹ Therefore, patients with PPS characterized by venous insufficiency may represent a population at increased risk for KS. 
 

Kaposi sarcoma (KS) is a low-grade vascular tumor that is rare among the general US population, with an incidence rate of less than 1 per 100,000.¹ The tumor is more common among certain groups of individuals due to geographic differences in the prevalence of KS-associated herpesvirus (also referred to as human herpesvirus 8) as well as host immune factors.² Kaposi sarcoma often is defined by the patient's predisposing characteristics yielding the following distinct epidemiologic subtypes: (1) classic KS is a rare disease affecting older men of Mediterranean descent; (2) African KS is an endemic cancer with male predominance in sub-Saharan Africa; (3) AIDS-associated KS is an often aggressive AIDS-defining illness; and (4) iatrogenic KS occurs in patients on immunosuppressive therapy.³ When evaluating a patient without any of these risk factors, the clinical suspicion for KS may be low. We report a patient with postpolio syndrome (PPS) who presented with KS of the right leg, ankle, and foot. 

A 77-year-old man with a distant history of paralytic poliomyelitis presented for an annual skin examination with concern for a new lesion on the right ankle. The patient had a history of PPS primarily affecting the right leg. Physical examination revealed residual weakness in an atrophic right lower extremity with a mottled appearance and mild pitting edema to the knee. Two red, dome-shaped, vascular papules were appreciated on the medial aspect of the right ankle (Figure 1), and a shave biopsy of the larger papule was performed. Microscopic examination of the biopsy specimen was consistent with KS (Figure 2). This patient had no history of human immunodeficiency virus or immunosuppressive therapy and was not of Mediterranean descent. 

Because KS is a radiosensitive vascular neoplasm and radiation therapy (RT) alone can achieve local control,⁴ the patient was treated with 6 megaelectron-volt electron-beam RT. He received 30 Gy in 10 fractions to the affected area of the medial ankle. The patient tolerated RT well. Three weeks after completing treatment, he was found to have mild lichenification on the right medial ankle with no clinical evidence of disease. Four months later, he presented with multiple additional vascular papules on the right third toe and in the interdigital web space (Figure 3). Shave biopsy of one of these lesions was consistent with KS. Contrast computed tomography of the chest, abdomen, and pelvis was performed, revealing no evidence of metastatic disease. The patient was treated with 30 Gy in 15 fractions using opposed lateral 6 megaelectron-volt photon fields to the entire right lower extremity below the knee to treat all of the skin affected by the PPS. His posttreatment course was complicated by edema in the affected leg that resolved after daily pneumatic compression. He had no evidence of residual or recurrent disease 6 months after completing RT (Figure 4). 

Cutaneous KS is a human herpesvirus 8-positive tumor of endothelial origin typically seen in older men of Mediterranean or African descent and among immunosuppressed patients.⁴ Our patient did not have any classic risk factors for KS, but his disease did arise in the setting of a right lower extremity that was notably affected by PPS. Postpolio syndrome is characterized by muscle atrophy due to denervation of the motor unit.⁵ Bruno et al⁶ found that such deficits in motor innervation could lead to impairments in venous outflow causing cutaneous venous congestion. Acroangiodermatitis clinically resembles KS but is a benign reactive vasoproliferative disorder and is well known to occur in the lower extremities as a sequela of chronic venous insufficiency.⁷ A case of bilateral lower extremity pseudo-KS was reported in a patient with notable PPS.⁸ A report of 2 patients describes KS arising in the setting of chronic venous insufficiency without any classic risk factors.⁹ Therefore, patients with PPS characterized by venous insufficiency may represent a population at increased risk for KS. 
 

The Diagnosis: Birt-Hogg-Dubé Syndrome 

Histopathologic examination revealed a collection of bland spindle cells with perifollicular fibrosis consistent with a fibrofolliculoma, confirming the diagnosis of Birt-Hogg-Dubé syndrome (Figure). Cosmetic treatment with ablative therapy was offered, but the patient declined.  

Birt-Hogg-Dubé syndrome is an autosomal-dominant genodermatosis caused by a loss-of-function mutation in the folliculin gene, FLCN, on chromosome arm 17p11.2.¹ Cutaneous findings include benign follicular hamartomas, such as fibrofolliculomas and trichodiscomas. Angiofibromas, perifollicular fibromas, oral papillomas, and acrochordons also can be present.¹ Cutaneous lesions usually appear on the head and neck in the third decade of life.  

Patients with Birt-Hogg-Dubé syndrome are at an increased risk for pneumothorax and renal cancer, specifically hybrid oncocytic-chromophobe renal cell carcinomas.² In a study of 89 patients with a FLCN mutation, 90% (80/89) of patients had cutaneous lesions, 84% (34/89) had pulmonary cysts, and 34% (30/89) had kidney tumors. Affected individuals were at a higher risk for pneumothorax and kidney tumors if there was a family history of these tumors.²  

Proposed diagnostic criteria include any 1 of the following: 2 or more skin lesions clinically consistent with fibrofolliculomas and 1 histologically confirmed fibrofolliculoma; multiple bilateral pulmonary cysts in the basilar lung with or without pneumothorax before 40 years of age; bilateral multifocal chromophobe renal carcinomas or hybrid oncocytic tumors; combination of cutaneous, pulmonary, or renal manifestation in the patient and family; or a FLCN mutation.³  

Current recommendations for the workup of a patient with Birt-Hogg-Dubé syndrome include referral to genetic counseling for the patient and family, a baseline computed tomography of the chest to evaluate for pulmonary cysts, and gadolinium-enhanced abdominal magnetic resonance imaging starting at 20 years of age and repeated every 3 to 4 years to screen for renal tumors.¹ Pulmonary function tests can be considered if the patient is symptomatic or has a high cyst burden. Patients should be advised against smoking and scuba diving. 

The differential diagnosis of multiple facial papules includes Cowden syndrome, tuberous sclerosis, Brooke-Spiegler syndrome, and Muir-Torre syndrome. Cowden syndrome is caused by a mutation in the protein tyrosine phosphatase gene, PTEN.⁴ The characteristic cutaneous findings on the face are trichilemmomas, which appear as flesh-colored papules that may have a verrucous surface.  

Tuberous sclerosis is caused by mutations in hamartin (TSC1) or tuberin (TSC2). Angiofibromas are most commonly found on the face and appear as flesh-colored to red-brown papules. Fibrous plaques, periungual fibromas, gingival fibromas, hypopigmented macules, and connective tissue nevi also are found in tuberous sclerosis.⁵  

Brooke-Spiegler syndrome is caused by a mutation in the CYLD lysine 63 deubiquitinase gene, CYLD. Trichoepitheliomas, cylindromas, and spiradenomas are caused by the CYLD mutation and appear on the head and neck. Trichoepitheliomas are flesh-colored to pink papules found on the face, often concentrated in the nasolabial folds.⁶ Cylindromas and spiradenomas are flesh-colored to pink papules or nodules most commonly found on the scalp.⁶  

Muir-Torre syndrome is caused by a mutation in DNA mismatch repair genes MSH2 and/or MLH1.⁷ Sebaceous neoplasms, including sebaceous adenomas, sebaceomas, and less frequently sebaceous carcinomas, are characteristic cutaneous findings and appear as pink to yellow papules commonly found on the head and neck.  

Careful history taking, physical examination, and histopathologic analysis are important in recognizing the features of Birt-Hogg-Dubé syndrome. Accurate and timely diagnosis is essential for the appropriate care of patients and their families, given the syndrome's systemic implications.  

The Diagnosis: Birt-Hogg-Dubé Syndrome 

Histopathologic examination revealed a collection of bland spindle cells with perifollicular fibrosis consistent with a fibrofolliculoma, confirming the diagnosis of Birt-Hogg-Dubé syndrome (Figure). Cosmetic treatment with ablative therapy was offered, but the patient declined.  

Birt-Hogg-Dubé syndrome is an autosomal-dominant genodermatosis caused by a loss-of-function mutation in the folliculin gene, FLCN, on chromosome arm 17p11.2.¹ Cutaneous findings include benign follicular hamartomas, such as fibrofolliculomas and trichodiscomas. Angiofibromas, perifollicular fibromas, oral papillomas, and acrochordons also can be present.¹ Cutaneous lesions usually appear on the head and neck in the third decade of life.  

Patients with Birt-Hogg-Dubé syndrome are at an increased risk for pneumothorax and renal cancer, specifically hybrid oncocytic-chromophobe renal cell carcinomas.² In a study of 89 patients with a FLCN mutation, 90% (80/89) of patients had cutaneous lesions, 84% (34/89) had pulmonary cysts, and 34% (30/89) had kidney tumors. Affected individuals were at a higher risk for pneumothorax and kidney tumors if there was a family history of these tumors.²  

Proposed diagnostic criteria include any 1 of the following: 2 or more skin lesions clinically consistent with fibrofolliculomas and 1 histologically confirmed fibrofolliculoma; multiple bilateral pulmonary cysts in the basilar lung with or without pneumothorax before 40 years of age; bilateral multifocal chromophobe renal carcinomas or hybrid oncocytic tumors; combination of cutaneous, pulmonary, or renal manifestation in the patient and family; or a FLCN mutation.³  

Current recommendations for the workup of a patient with Birt-Hogg-Dubé syndrome include referral to genetic counseling for the patient and family, a baseline computed tomography of the chest to evaluate for pulmonary cysts, and gadolinium-enhanced abdominal magnetic resonance imaging starting at 20 years of age and repeated every 3 to 4 years to screen for renal tumors.¹ Pulmonary function tests can be considered if the patient is symptomatic or has a high cyst burden. Patients should be advised against smoking and scuba diving. 

The differential diagnosis of multiple facial papules includes Cowden syndrome, tuberous sclerosis, Brooke-Spiegler syndrome, and Muir-Torre syndrome. Cowden syndrome is caused by a mutation in the protein tyrosine phosphatase gene, PTEN.⁴ The characteristic cutaneous findings on the face are trichilemmomas, which appear as flesh-colored papules that may have a verrucous surface.  

Tuberous sclerosis is caused by mutations in hamartin (TSC1) or tuberin (TSC2). Angiofibromas are most commonly found on the face and appear as flesh-colored to red-brown papules. Fibrous plaques, periungual fibromas, gingival fibromas, hypopigmented macules, and connective tissue nevi also are found in tuberous sclerosis.⁵  

Brooke-Spiegler syndrome is caused by a mutation in the CYLD lysine 63 deubiquitinase gene, CYLD. Trichoepitheliomas, cylindromas, and spiradenomas are caused by the CYLD mutation and appear on the head and neck. Trichoepitheliomas are flesh-colored to pink papules found on the face, often concentrated in the nasolabial folds.⁶ Cylindromas and spiradenomas are flesh-colored to pink papules or nodules most commonly found on the scalp.⁶  

Muir-Torre syndrome is caused by a mutation in DNA mismatch repair genes MSH2 and/or MLH1.⁷ Sebaceous neoplasms, including sebaceous adenomas, sebaceomas, and less frequently sebaceous carcinomas, are characteristic cutaneous findings and appear as pink to yellow papules commonly found on the head and neck.  

Careful history taking, physical examination, and histopathologic analysis are important in recognizing the features of Birt-Hogg-Dubé syndrome. Accurate and timely diagnosis is essential for the appropriate care of patients and their families, given the syndrome's systemic implications.  

The Diagnosis: Birt-Hogg-Dubé Syndrome 

Histopathologic examination revealed a collection of bland spindle cells with perifollicular fibrosis consistent with a fibrofolliculoma, confirming the diagnosis of Birt-Hogg-Dubé syndrome (Figure). Cosmetic treatment with ablative therapy was offered, but the patient declined.  

Birt-Hogg-Dubé syndrome is an autosomal-dominant genodermatosis caused by a loss-of-function mutation in the folliculin gene, FLCN, on chromosome arm 17p11.2.¹ Cutaneous findings include benign follicular hamartomas, such as fibrofolliculomas and trichodiscomas. Angiofibromas, perifollicular fibromas, oral papillomas, and acrochordons also can be present.¹ Cutaneous lesions usually appear on the head and neck in the third decade of life.  

Patients with Birt-Hogg-Dubé syndrome are at an increased risk for pneumothorax and renal cancer, specifically hybrid oncocytic-chromophobe renal cell carcinomas.² In a study of 89 patients with a FLCN mutation, 90% (80/89) of patients had cutaneous lesions, 84% (34/89) had pulmonary cysts, and 34% (30/89) had kidney tumors. Affected individuals were at a higher risk for pneumothorax and kidney tumors if there was a family history of these tumors.²  

Proposed diagnostic criteria include any 1 of the following: 2 or more skin lesions clinically consistent with fibrofolliculomas and 1 histologically confirmed fibrofolliculoma; multiple bilateral pulmonary cysts in the basilar lung with or without pneumothorax before 40 years of age; bilateral multifocal chromophobe renal carcinomas or hybrid oncocytic tumors; combination of cutaneous, pulmonary, or renal manifestation in the patient and family; or a FLCN mutation.³  

Current recommendations for the workup of a patient with Birt-Hogg-Dubé syndrome include referral to genetic counseling for the patient and family, a baseline computed tomography of the chest to evaluate for pulmonary cysts, and gadolinium-enhanced abdominal magnetic resonance imaging starting at 20 years of age and repeated every 3 to 4 years to screen for renal tumors.¹ Pulmonary function tests can be considered if the patient is symptomatic or has a high cyst burden. Patients should be advised against smoking and scuba diving. 

The differential diagnosis of multiple facial papules includes Cowden syndrome, tuberous sclerosis, Brooke-Spiegler syndrome, and Muir-Torre syndrome. Cowden syndrome is caused by a mutation in the protein tyrosine phosphatase gene, PTEN.⁴ The characteristic cutaneous findings on the face are trichilemmomas, which appear as flesh-colored papules that may have a verrucous surface.  

Tuberous sclerosis is caused by mutations in hamartin (TSC1) or tuberin (TSC2). Angiofibromas are most commonly found on the face and appear as flesh-colored to red-brown papules. Fibrous plaques, periungual fibromas, gingival fibromas, hypopigmented macules, and connective tissue nevi also are found in tuberous sclerosis.⁵  

Brooke-Spiegler syndrome is caused by a mutation in the CYLD lysine 63 deubiquitinase gene, CYLD. Trichoepitheliomas, cylindromas, and spiradenomas are caused by the CYLD mutation and appear on the head and neck. Trichoepitheliomas are flesh-colored to pink papules found on the face, often concentrated in the nasolabial folds.⁶ Cylindromas and spiradenomas are flesh-colored to pink papules or nodules most commonly found on the scalp.⁶  

Muir-Torre syndrome is caused by a mutation in DNA mismatch repair genes MSH2 and/or MLH1.⁷ Sebaceous neoplasms, including sebaceous adenomas, sebaceomas, and less frequently sebaceous carcinomas, are characteristic cutaneous findings and appear as pink to yellow papules commonly found on the head and neck.  

Careful history taking, physical examination, and histopathologic analysis are important in recognizing the features of Birt-Hogg-Dubé syndrome. Accurate and timely diagnosis is essential for the appropriate care of patients and their families, given the syndrome's systemic implications.  

The Diagnosis: Mosaic Tuberous Sclerosis 

A punch biopsy of the facial lesion was stained with hematoxylin and eosin, which demonstrated spindled and stellate fibroblasts with dilated blood vessels (Figure), consistent with an angiofibroma. Given the clinical presentation and histologic findings, there was concern for a diagnosis of tuberous sclerosis (TSC). The patient was referred for genetic workup but tested negative for mutations of the TSC genes in the blood. Because the patient had only unilateral facial lesions, a possible cortical tuber, no other symptoms, and tested negative for TSC gene mutations, mosaic TSC was considered a likely diagnosis. Her facial lesions were treated with pulsed dye vascular laser therapy. 

Tuberous sclerosis is an autosomal-dominant neurocutaneous disorder caused by inactivation of the genes TSC1 (encoding hamartin) and TSC2 (encoding tuberin). Mutation results in overactivation of the downstream mTOR (mammalian target of rapamycin) pathway, resulting in abnormal cellular proliferation and hamartomas. These benign tumors can be found in nearly every organ, most often in the central nervous system and skin, and they provide for a highly variable presentation of the disease.¹ 

Tuberous sclerosis affects 1 in 6000 to 10,000 live births and has a prevalence of 1 in 20,000 individuals. Of these individuals, 75% carry sporadic mutations, and 75% to 90% eventually test positive for a TSC gene mutation.² Genetic mosaicism has been reported in 28% of cases affected by large deletions¹ and as few as 1% of cases involving small mutations.³ 

The dermatologic manifestation of mosaic TSC most often includes unilateral angiofibromas, whereas in nonmosaic cases, angiofibromas cover both cheeks, the forehead, and the eyelids. The other skin lesions of TSC--shagreen patches, forehead plaques, hypomelanotic macules, and ungual fibromas--are seen less frequently.^4-6 Additionally, neurologic disease in mosaic patients is notably milder, with 57% of mosaic patients found to have epilepsy compared to 91% of nonmosaic patients.⁷ Our patient had both unilateral facial angiofibromas and a cortical lesion suspicious for a tuber, prompting a suspected diagnosis of mosaic TSC. 

The methods of diagnosis outlined by the International Tuberous Sclerosis Complex Consensus Group pose a challenge in diagnosing mosaic TSC. The clinical criteria require 2 major (eg, multiple angiofibromas, angiomyolipomas, a shagreen patch) and 1 minor feature (eg, dental enamel pit, renal cyst).² However, case reports detailing unilateral facial angiofibromas have described patients with isolated dermatologic findings.^5,6 Further, it has been demonstrated that genetic studies in mosaic TSC can be unreliable depending on the tissue sampled.⁸ Thus, for patients who have mosaic TSC, establishing a definitive diagnosis is not always possible and may rely solely on the clinical picture. 

Considering the differential diagnosis, benign cephalic histiocytosis usually would present with small red-brown macules and papules symmetrically located on the head and neck. The lesions occur at a younger age, usually in the first year or two of life. Fibrofolliculomas present as multiple whitish, slightly larger papules found on the central face. They are a marker for Birt-Hogg-Dubé syndrome, which also is associated with spontaneous pneumothorax.  

Agminated means clustering or grouping of lesions. Agminated melanocytic nevi and agminated Spitz nevi are clusters of nevi. These lesions can vary in size and color. They may be elevated or flat. Melanocytic nevi usually are tan-brown or black. Spitz nevi may be pink or pigmented brown or black. To definitively differentiate between these 2 diagnoses and this patient's diagnosis of angiofibroma, a biopsy is needed.

The Diagnosis: Mosaic Tuberous Sclerosis 

A punch biopsy of the facial lesion was stained with hematoxylin and eosin, which demonstrated spindled and stellate fibroblasts with dilated blood vessels (Figure), consistent with an angiofibroma. Given the clinical presentation and histologic findings, there was concern for a diagnosis of tuberous sclerosis (TSC). The patient was referred for genetic workup but tested negative for mutations of the TSC genes in the blood. Because the patient had only unilateral facial lesions, a possible cortical tuber, no other symptoms, and tested negative for TSC gene mutations, mosaic TSC was considered a likely diagnosis. Her facial lesions were treated with pulsed dye vascular laser therapy. 

Tuberous sclerosis is an autosomal-dominant neurocutaneous disorder caused by inactivation of the genes TSC1 (encoding hamartin) and TSC2 (encoding tuberin). Mutation results in overactivation of the downstream mTOR (mammalian target of rapamycin) pathway, resulting in abnormal cellular proliferation and hamartomas. These benign tumors can be found in nearly every organ, most often in the central nervous system and skin, and they provide for a highly variable presentation of the disease.¹ 

Tuberous sclerosis affects 1 in 6000 to 10,000 live births and has a prevalence of 1 in 20,000 individuals. Of these individuals, 75% carry sporadic mutations, and 75% to 90% eventually test positive for a TSC gene mutation.² Genetic mosaicism has been reported in 28% of cases affected by large deletions¹ and as few as 1% of cases involving small mutations.³ 

The dermatologic manifestation of mosaic TSC most often includes unilateral angiofibromas, whereas in nonmosaic cases, angiofibromas cover both cheeks, the forehead, and the eyelids. The other skin lesions of TSC--shagreen patches, forehead plaques, hypomelanotic macules, and ungual fibromas--are seen less frequently.^4-6 Additionally, neurologic disease in mosaic patients is notably milder, with 57% of mosaic patients found to have epilepsy compared to 91% of nonmosaic patients.⁷ Our patient had both unilateral facial angiofibromas and a cortical lesion suspicious for a tuber, prompting a suspected diagnosis of mosaic TSC. 

The methods of diagnosis outlined by the International Tuberous Sclerosis Complex Consensus Group pose a challenge in diagnosing mosaic TSC. The clinical criteria require 2 major (eg, multiple angiofibromas, angiomyolipomas, a shagreen patch) and 1 minor feature (eg, dental enamel pit, renal cyst).² However, case reports detailing unilateral facial angiofibromas have described patients with isolated dermatologic findings.^5,6 Further, it has been demonstrated that genetic studies in mosaic TSC can be unreliable depending on the tissue sampled.⁸ Thus, for patients who have mosaic TSC, establishing a definitive diagnosis is not always possible and may rely solely on the clinical picture. 

Considering the differential diagnosis, benign cephalic histiocytosis usually would present with small red-brown macules and papules symmetrically located on the head and neck. The lesions occur at a younger age, usually in the first year or two of life. Fibrofolliculomas present as multiple whitish, slightly larger papules found on the central face. They are a marker for Birt-Hogg-Dubé syndrome, which also is associated with spontaneous pneumothorax.  

Agminated means clustering or grouping of lesions. Agminated melanocytic nevi and agminated Spitz nevi are clusters of nevi. These lesions can vary in size and color. They may be elevated or flat. Melanocytic nevi usually are tan-brown or black. Spitz nevi may be pink or pigmented brown or black. To definitively differentiate between these 2 diagnoses and this patient's diagnosis of angiofibroma, a biopsy is needed.

The Diagnosis: Mosaic Tuberous Sclerosis 

A punch biopsy of the facial lesion was stained with hematoxylin and eosin, which demonstrated spindled and stellate fibroblasts with dilated blood vessels (Figure), consistent with an angiofibroma. Given the clinical presentation and histologic findings, there was concern for a diagnosis of tuberous sclerosis (TSC). The patient was referred for genetic workup but tested negative for mutations of the TSC genes in the blood. Because the patient had only unilateral facial lesions, a possible cortical tuber, no other symptoms, and tested negative for TSC gene mutations, mosaic TSC was considered a likely diagnosis. Her facial lesions were treated with pulsed dye vascular laser therapy. 

Tuberous sclerosis is an autosomal-dominant neurocutaneous disorder caused by inactivation of the genes TSC1 (encoding hamartin) and TSC2 (encoding tuberin). Mutation results in overactivation of the downstream mTOR (mammalian target of rapamycin) pathway, resulting in abnormal cellular proliferation and hamartomas. These benign tumors can be found in nearly every organ, most often in the central nervous system and skin, and they provide for a highly variable presentation of the disease.¹ 

Tuberous sclerosis affects 1 in 6000 to 10,000 live births and has a prevalence of 1 in 20,000 individuals. Of these individuals, 75% carry sporadic mutations, and 75% to 90% eventually test positive for a TSC gene mutation.² Genetic mosaicism has been reported in 28% of cases affected by large deletions¹ and as few as 1% of cases involving small mutations.³ 

The dermatologic manifestation of mosaic TSC most often includes unilateral angiofibromas, whereas in nonmosaic cases, angiofibromas cover both cheeks, the forehead, and the eyelids. The other skin lesions of TSC--shagreen patches, forehead plaques, hypomelanotic macules, and ungual fibromas--are seen less frequently.^4-6 Additionally, neurologic disease in mosaic patients is notably milder, with 57% of mosaic patients found to have epilepsy compared to 91% of nonmosaic patients.⁷ Our patient had both unilateral facial angiofibromas and a cortical lesion suspicious for a tuber, prompting a suspected diagnosis of mosaic TSC. 

The methods of diagnosis outlined by the International Tuberous Sclerosis Complex Consensus Group pose a challenge in diagnosing mosaic TSC. The clinical criteria require 2 major (eg, multiple angiofibromas, angiomyolipomas, a shagreen patch) and 1 minor feature (eg, dental enamel pit, renal cyst).² However, case reports detailing unilateral facial angiofibromas have described patients with isolated dermatologic findings.^5,6 Further, it has been demonstrated that genetic studies in mosaic TSC can be unreliable depending on the tissue sampled.⁸ Thus, for patients who have mosaic TSC, establishing a definitive diagnosis is not always possible and may rely solely on the clinical picture. 

Considering the differential diagnosis, benign cephalic histiocytosis usually would present with small red-brown macules and papules symmetrically located on the head and neck. The lesions occur at a younger age, usually in the first year or two of life. Fibrofolliculomas present as multiple whitish, slightly larger papules found on the central face. They are a marker for Birt-Hogg-Dubé syndrome, which also is associated with spontaneous pneumothorax.  

Agminated means clustering or grouping of lesions. Agminated melanocytic nevi and agminated Spitz nevi are clusters of nevi. These lesions can vary in size and color. They may be elevated or flat. Melanocytic nevi usually are tan-brown or black. Spitz nevi may be pink or pigmented brown or black. To definitively differentiate between these 2 diagnoses and this patient's diagnosis of angiofibroma, a biopsy is needed.

The Diagnosis: Sclerosing Perineurioma 

Sclerosing perineurioma, first described in 1997 by Fetsch and Miettinen,¹ is a subtype of perineurioma with a strong predilection for the fingers and palms of young adults. Rare cases involving extra-acral sites including the forearm, elbow, axilla, back, neck, lower leg, thigh, knee, lips, nose, and mouth have been reported.^2-4 Perineurioma is a relatively uncommon and benign peripheral nerve sheath tumor with exclusive perineurial differentiation.⁵ Perineurioma is divided into intraneural and extraneural types; the latter are further subclassified into soft tissue, sclerosing, reticular, and plexiform types. Other rare forms include the sclerosing, Pacinian corpuscle-like perineurioma, lipomatous perineurioma, perineurioma with xanthomatous areas, and perineurioma with granular cells.^6,7  

Clinically, sclerosing perineurioma usually presents as a solitary lesion; however, rare cases of multiple lesions have been reported.⁸ Our patient presented with a solitary papule on the nose. Histopathologically, sclerosing perineurioma demonstrates slender spindle cells in a whorled growth pattern (onion skin) embedded in a hyalinized, lamellar, and dense collagenous stroma with intervening cleftlike spaces. Immunohistochemically, the spindle cells of our case stained positive for epithelial membrane antigen (quiz images). Other positive immunostains for perineurioma include claudin-1 and glucose transporter 1 (GLUT1). Perineurioma lacks expression of S-100 but can express CD34.² As a benign tumor, the prognosis of sclerosing perineurioma is excellent. Complete local excision is considered curative.¹  

Angiofibroma, also known as fibrous papule, is a common and benign lesion located primarily on or in close proximity to the nose.⁹ Angiofibromas can be associated with genodermatoses such as tuberous sclerosis, multiple endocrine neoplasia type 1, or Birt-Hogg-Dubé syndrome. When angiofibromas involve the penis, they are called pearly penile papules. Ungual angiofibroma, also known as Koenen tumor, occurs underneath the nail.^10-12 Both facial angiofibromas (>3) and ungual angiofibromas (>2) are independent major criteria for tuberous sclerosis.¹³ Clinically, angiofibroma presents as a small, dome-shaped, pink papule arising on the lower portion of the nose or nearby area of the central face. Histopathologically, angiofibromas classically demonstrate increased dilated vessels and fibrosis in the dermis. Stellate, plump, spindle-shaped, and multinucleated cells can be seen in the collagenous stroma. The collagen fibers around hair follicles are arranged concentrically, resulting in an onion skin-like appearance. The epidermal rete ridges can be effaced (Figure 1). Increased numbers of single-unit melanocytes along the dermoepidermal junction can be seen in some cases. Immunohistochemically, a variable number of spindled and multinucleated cells in the dermis stain with factor XIIIa. There are at least 7 histologic variants of angiofibroma including hypercellular, pigmented, inflammatory, pleomorphic, clear cell, granular cell, and epithelioid.^9,14 

Desmoplastic nevus (DN) is a benign melanocytic neoplasm characterized by predominantly spindle-shaped nevus cells embedded within a fibrotic stroma. Although it can resemble a Spitz nevus, it is recognized as a distinct entity.^15-17 Clinically, DN presents as a small and flesh-colored, erythematous or slightly pigmented papule or nodule that usually occurs on the arms and legs of young adults. Histopathologically, DN demonstrates a dermal-based proliferation of spindled melanocytes embedded in a dense collagenous stroma with sparse or absent melanin deposition. The collagen bundles often show artifactual clefts and onion skin-like accentuation around vessels. Melanocytes may be epithelioid (Figure 2).¹⁶ Immunohistochemically, DN expresses melanocytic markers such as S-100, Melan-A, and human melanoma black 45, but epithelial membrane antigen is negative. Human melanoma black 45 demonstrates maturation with stronger staining in superficial portions of the lesion and diminution of staining with increasing dermal depth.¹⁸ Many other melanocytic tumors share histologic similarities to DN including blue nevus and desmoplastic melanoma.^17,19,20  

Palisaded encapsulated neuroma, also referred to as solitary circumscribed neuroma, was first described by Reed et al²¹ in 1972. It is a benign and solitary, firm, dome-shaped, flesh-colored papule that occurs in middle-aged adults, predominately near mucocutaneous junctions of the face. Other locations include the oral mucosa, eyelid, nasal fossa, shoulder, arm, hand, foot, and glans penis.^22,23 Histopathologically, palisaded encapsulated neuroma demonstrates a solitary, well-circumscribed, partially encapsulated, intradermal nodule composed of interweaving fascicles of spindle cells with prominent clefts (Figure 3). Rarely, palisaded encapsulated neuroma may have a plexiform or multinodular architecture.²⁴ Immunohistochemically, tumor cells stain positively for S-100 protein, type IV collagen, and vimentin. The capsule, composed of perineural cells, stains positive for epithelial membrane antigen. A neurofilament stain will highlight axons within the tumor.^24,25 Currently, palisaded encapsulated neuroma does not have a well-established link to known neurocutaneous or inherited syndromes. Excision is curative with a low risk of recurrence.²⁶ 

Sclerotic fibromas (SFs) were first reported by Weary et al²⁷ as multiple tumors involving the tongues of patients with Cowden syndrome. Sporadic or solitary SFs of the skin in patients without Cowden syndrome have been reported, and both multiple and solitary SFs present with similar pathologic changes.^28-30 Clinically, the solitary variant manifests as a well-demarcated, flesh-colored to erythematous, waxy papule or nodule with no site or sex predilection.^30,31 Histologically, SF demonstrates a well-demarcated, nonencapsulated dermal nodule composed of hypocellular and sclerotic collagen bundles with scattered spindled cells and prominent clefts resembling Vincent van Gogh's Starry Night or plywood (Figure 4). Immunohistochemically, the spindled cells strongly express CD34. Factor XIIIa and markers of melanocytic, neural, and muscular differentiation are negative. When rendering a diagnosis in a patient with multiple SFs, a comment regarding the possibility of Cowden syndrome should be mentioned.³² 

The Diagnosis: Sclerosing Perineurioma 

Sclerosing perineurioma, first described in 1997 by Fetsch and Miettinen,¹ is a subtype of perineurioma with a strong predilection for the fingers and palms of young adults. Rare cases involving extra-acral sites including the forearm, elbow, axilla, back, neck, lower leg, thigh, knee, lips, nose, and mouth have been reported.^2-4 Perineurioma is a relatively uncommon and benign peripheral nerve sheath tumor with exclusive perineurial differentiation.⁵ Perineurioma is divided into intraneural and extraneural types; the latter are further subclassified into soft tissue, sclerosing, reticular, and plexiform types. Other rare forms include the sclerosing, Pacinian corpuscle-like perineurioma, lipomatous perineurioma, perineurioma with xanthomatous areas, and perineurioma with granular cells.^6,7  

Clinically, sclerosing perineurioma usually presents as a solitary lesion; however, rare cases of multiple lesions have been reported.⁸ Our patient presented with a solitary papule on the nose. Histopathologically, sclerosing perineurioma demonstrates slender spindle cells in a whorled growth pattern (onion skin) embedded in a hyalinized, lamellar, and dense collagenous stroma with intervening cleftlike spaces. Immunohistochemically, the spindle cells of our case stained positive for epithelial membrane antigen (quiz images). Other positive immunostains for perineurioma include claudin-1 and glucose transporter 1 (GLUT1). Perineurioma lacks expression of S-100 but can express CD34.² As a benign tumor, the prognosis of sclerosing perineurioma is excellent. Complete local excision is considered curative.¹  

Angiofibroma, also known as fibrous papule, is a common and benign lesion located primarily on or in close proximity to the nose.⁹ Angiofibromas can be associated with genodermatoses such as tuberous sclerosis, multiple endocrine neoplasia type 1, or Birt-Hogg-Dubé syndrome. When angiofibromas involve the penis, they are called pearly penile papules. Ungual angiofibroma, also known as Koenen tumor, occurs underneath the nail.^10-12 Both facial angiofibromas (>3) and ungual angiofibromas (>2) are independent major criteria for tuberous sclerosis.¹³ Clinically, angiofibroma presents as a small, dome-shaped, pink papule arising on the lower portion of the nose or nearby area of the central face. Histopathologically, angiofibromas classically demonstrate increased dilated vessels and fibrosis in the dermis. Stellate, plump, spindle-shaped, and multinucleated cells can be seen in the collagenous stroma. The collagen fibers around hair follicles are arranged concentrically, resulting in an onion skin-like appearance. The epidermal rete ridges can be effaced (Figure 1). Increased numbers of single-unit melanocytes along the dermoepidermal junction can be seen in some cases. Immunohistochemically, a variable number of spindled and multinucleated cells in the dermis stain with factor XIIIa. There are at least 7 histologic variants of angiofibroma including hypercellular, pigmented, inflammatory, pleomorphic, clear cell, granular cell, and epithelioid.^9,14 

Desmoplastic nevus (DN) is a benign melanocytic neoplasm characterized by predominantly spindle-shaped nevus cells embedded within a fibrotic stroma. Although it can resemble a Spitz nevus, it is recognized as a distinct entity.^15-17 Clinically, DN presents as a small and flesh-colored, erythematous or slightly pigmented papule or nodule that usually occurs on the arms and legs of young adults. Histopathologically, DN demonstrates a dermal-based proliferation of spindled melanocytes embedded in a dense collagenous stroma with sparse or absent melanin deposition. The collagen bundles often show artifactual clefts and onion skin-like accentuation around vessels. Melanocytes may be epithelioid (Figure 2).¹⁶ Immunohistochemically, DN expresses melanocytic markers such as S-100, Melan-A, and human melanoma black 45, but epithelial membrane antigen is negative. Human melanoma black 45 demonstrates maturation with stronger staining in superficial portions of the lesion and diminution of staining with increasing dermal depth.¹⁸ Many other melanocytic tumors share histologic similarities to DN including blue nevus and desmoplastic melanoma.^17,19,20  

Palisaded encapsulated neuroma, also referred to as solitary circumscribed neuroma, was first described by Reed et al²¹ in 1972. It is a benign and solitary, firm, dome-shaped, flesh-colored papule that occurs in middle-aged adults, predominately near mucocutaneous junctions of the face. Other locations include the oral mucosa, eyelid, nasal fossa, shoulder, arm, hand, foot, and glans penis.^22,23 Histopathologically, palisaded encapsulated neuroma demonstrates a solitary, well-circumscribed, partially encapsulated, intradermal nodule composed of interweaving fascicles of spindle cells with prominent clefts (Figure 3). Rarely, palisaded encapsulated neuroma may have a plexiform or multinodular architecture.²⁴ Immunohistochemically, tumor cells stain positively for S-100 protein, type IV collagen, and vimentin. The capsule, composed of perineural cells, stains positive for epithelial membrane antigen. A neurofilament stain will highlight axons within the tumor.^24,25 Currently, palisaded encapsulated neuroma does not have a well-established link to known neurocutaneous or inherited syndromes. Excision is curative with a low risk of recurrence.²⁶ 

Sclerotic fibromas (SFs) were first reported by Weary et al²⁷ as multiple tumors involving the tongues of patients with Cowden syndrome. Sporadic or solitary SFs of the skin in patients without Cowden syndrome have been reported, and both multiple and solitary SFs present with similar pathologic changes.^28-30 Clinically, the solitary variant manifests as a well-demarcated, flesh-colored to erythematous, waxy papule or nodule with no site or sex predilection.^30,31 Histologically, SF demonstrates a well-demarcated, nonencapsulated dermal nodule composed of hypocellular and sclerotic collagen bundles with scattered spindled cells and prominent clefts resembling Vincent van Gogh's Starry Night or plywood (Figure 4). Immunohistochemically, the spindled cells strongly express CD34. Factor XIIIa and markers of melanocytic, neural, and muscular differentiation are negative. When rendering a diagnosis in a patient with multiple SFs, a comment regarding the possibility of Cowden syndrome should be mentioned.³² 

The Diagnosis: Sclerosing Perineurioma 

Sclerosing perineurioma, first described in 1997 by Fetsch and Miettinen,¹ is a subtype of perineurioma with a strong predilection for the fingers and palms of young adults. Rare cases involving extra-acral sites including the forearm, elbow, axilla, back, neck, lower leg, thigh, knee, lips, nose, and mouth have been reported.^2-4 Perineurioma is a relatively uncommon and benign peripheral nerve sheath tumor with exclusive perineurial differentiation.⁵ Perineurioma is divided into intraneural and extraneural types; the latter are further subclassified into soft tissue, sclerosing, reticular, and plexiform types. Other rare forms include the sclerosing, Pacinian corpuscle-like perineurioma, lipomatous perineurioma, perineurioma with xanthomatous areas, and perineurioma with granular cells.^6,7  

Clinically, sclerosing perineurioma usually presents as a solitary lesion; however, rare cases of multiple lesions have been reported.⁸ Our patient presented with a solitary papule on the nose. Histopathologically, sclerosing perineurioma demonstrates slender spindle cells in a whorled growth pattern (onion skin) embedded in a hyalinized, lamellar, and dense collagenous stroma with intervening cleftlike spaces. Immunohistochemically, the spindle cells of our case stained positive for epithelial membrane antigen (quiz images). Other positive immunostains for perineurioma include claudin-1 and glucose transporter 1 (GLUT1). Perineurioma lacks expression of S-100 but can express CD34.² As a benign tumor, the prognosis of sclerosing perineurioma is excellent. Complete local excision is considered curative.¹  

Angiofibroma, also known as fibrous papule, is a common and benign lesion located primarily on or in close proximity to the nose.⁹ Angiofibromas can be associated with genodermatoses such as tuberous sclerosis, multiple endocrine neoplasia type 1, or Birt-Hogg-Dubé syndrome. When angiofibromas involve the penis, they are called pearly penile papules. Ungual angiofibroma, also known as Koenen tumor, occurs underneath the nail.^10-12 Both facial angiofibromas (>3) and ungual angiofibromas (>2) are independent major criteria for tuberous sclerosis.¹³ Clinically, angiofibroma presents as a small, dome-shaped, pink papule arising on the lower portion of the nose or nearby area of the central face. Histopathologically, angiofibromas classically demonstrate increased dilated vessels and fibrosis in the dermis. Stellate, plump, spindle-shaped, and multinucleated cells can be seen in the collagenous stroma. The collagen fibers around hair follicles are arranged concentrically, resulting in an onion skin-like appearance. The epidermal rete ridges can be effaced (Figure 1). Increased numbers of single-unit melanocytes along the dermoepidermal junction can be seen in some cases. Immunohistochemically, a variable number of spindled and multinucleated cells in the dermis stain with factor XIIIa. There are at least 7 histologic variants of angiofibroma including hypercellular, pigmented, inflammatory, pleomorphic, clear cell, granular cell, and epithelioid.^9,14 

Desmoplastic nevus (DN) is a benign melanocytic neoplasm characterized by predominantly spindle-shaped nevus cells embedded within a fibrotic stroma. Although it can resemble a Spitz nevus, it is recognized as a distinct entity.^15-17 Clinically, DN presents as a small and flesh-colored, erythematous or slightly pigmented papule or nodule that usually occurs on the arms and legs of young adults. Histopathologically, DN demonstrates a dermal-based proliferation of spindled melanocytes embedded in a dense collagenous stroma with sparse or absent melanin deposition. The collagen bundles often show artifactual clefts and onion skin-like accentuation around vessels. Melanocytes may be epithelioid (Figure 2).¹⁶ Immunohistochemically, DN expresses melanocytic markers such as S-100, Melan-A, and human melanoma black 45, but epithelial membrane antigen is negative. Human melanoma black 45 demonstrates maturation with stronger staining in superficial portions of the lesion and diminution of staining with increasing dermal depth.¹⁸ Many other melanocytic tumors share histologic similarities to DN including blue nevus and desmoplastic melanoma.^17,19,20  

Palisaded encapsulated neuroma, also referred to as solitary circumscribed neuroma, was first described by Reed et al²¹ in 1972. It is a benign and solitary, firm, dome-shaped, flesh-colored papule that occurs in middle-aged adults, predominately near mucocutaneous junctions of the face. Other locations include the oral mucosa, eyelid, nasal fossa, shoulder, arm, hand, foot, and glans penis.^22,23 Histopathologically, palisaded encapsulated neuroma demonstrates a solitary, well-circumscribed, partially encapsulated, intradermal nodule composed of interweaving fascicles of spindle cells with prominent clefts (Figure 3). Rarely, palisaded encapsulated neuroma may have a plexiform or multinodular architecture.²⁴ Immunohistochemically, tumor cells stain positively for S-100 protein, type IV collagen, and vimentin. The capsule, composed of perineural cells, stains positive for epithelial membrane antigen. A neurofilament stain will highlight axons within the tumor.^24,25 Currently, palisaded encapsulated neuroma does not have a well-established link to known neurocutaneous or inherited syndromes. Excision is curative with a low risk of recurrence.²⁶ 

Sclerotic fibromas (SFs) were first reported by Weary et al²⁷ as multiple tumors involving the tongues of patients with Cowden syndrome. Sporadic or solitary SFs of the skin in patients without Cowden syndrome have been reported, and both multiple and solitary SFs present with similar pathologic changes.^28-30 Clinically, the solitary variant manifests as a well-demarcated, flesh-colored to erythematous, waxy papule or nodule with no site or sex predilection.^30,31 Histologically, SF demonstrates a well-demarcated, nonencapsulated dermal nodule composed of hypocellular and sclerotic collagen bundles with scattered spindled cells and prominent clefts resembling Vincent van Gogh's Starry Night or plywood (Figure 4). Immunohistochemically, the spindled cells strongly express CD34. Factor XIIIa and markers of melanocytic, neural, and muscular differentiation are negative. When rendering a diagnosis in a patient with multiple SFs, a comment regarding the possibility of Cowden syndrome should be mentioned.³² 

 

Case Report

A 7-year-old Chinese boy presented with multiple painful oral and tongue ulcers of 2 weeks’ duration as well as acute onset of moderate to high fever (highest temperature, 39.3°C) for 5 days. The fever was reported to have run a relapsing course, accompanied by rigors but without convulsions or cognitive changes. At times, the patient had nasal congestion, nasal discharge, and cough. He also had a transient eruption on the back and hands as well as an indurated red nodule on the left forearm.

Before the patient was hospitalized, antibiotic therapy was administered by other physicians, but the condition of fever and oral ulcers did not improve. After the patient was hospitalized, new tender nodules emerged on the scalp, buttocks, and lower extremities. New ulcers also appeared on the palate.

History
Two months earlier, the patient had presented with a painful perioral skin ulcer that resolved after being treated as contagious eczema. Another dermatologist previously had considered a diagnosis of hand-foot-and-mouth disease.

The patient was born by normal spontaneous vaginal delivery, without abnormality. He was breastfed; feeding, growth, and the developmental history showed no abnormality. He was the family’s eldest child, with a healthy brother and sister. There was no history of familial illness. He received bacillus Calmette-Guérin and poliomyelitis vaccines after birth; the rest of the vaccine history was unclear. There was no history of immunologic abnormality.

Physical Examination
A 1.5×1.5-cm, warm, red nodule with a central black crust was noted on the left forearm (Figure 1A). Several similar lesions were noted on the buttocks, scalp, and lower extremities. Multiple ulcers, as large as 1 cm, were present on the tongue, palate, and left angle of the mouth (Figure 1B). The pharynx was congested, and the tonsils were mildly enlarged. Multiple enlarged, movable, nontender lymph nodes could be palpated in the cervical basins, axillae, and groin. No purpura or ecchymosis was detected.

 

 

Laboratory Results
Laboratory testing revealed a normal total white blood cell count (4.26×10⁹/L [reference range, 4.0–12.0×10⁹/L]), with normal neutrophils (1.36×10⁹/L [reference range, 1.32–7.90×10⁹/L]), lymphocytes (2.77×10⁹/L [reference range, 1.20–6.00×10⁹/L]), and monocytes (0.13×10⁹/L [reference range, 0.08–0.80×10⁹/L]); a mildly decreased hemoglobin level (115 g/L [reference range, 120–160 g/L]); a normal platelet count (102×10⁹/L [reference range, 100–380×10⁹/L]); an elevated lactate dehydrogenase level (614 U/L [reference range, 110–330 U/L]); an elevated α-hydroxybutyrate dehydrogenase level (483 U/L [reference range, 120–270 U/L]); elevated prothrombin time (15.3 s [reference range, 9–14 s]); elevated activated partial thromboplastin time (59.8 s [reference range, 20.6–39.6 s]); and an elevated D-dimer level (1.51 mg/L [reference range, <0.73 mg/L]). In addition, autoantibody testing revealed a positive antinuclear antibody titer of 1:320 and a strong positive anti–Ro-52 level.

The peripheral blood lymphocyte classification demonstrated a prominent elevated percentage of T lymphocytes, with predominantly CD8⁺ cells (CD3, 94.87%; CD8, 71.57%; CD4, 24.98%; CD4:CD8 ratio, 0.35) and a diminished percentage of B lymphocytes and natural killer (NK) cells. Epstein-Barr virus (EBV) antibody testing was positive for anti–viral capsid antigen (VCA) IgG and negative for anti-VCA IgM.

Smears of the ulcer on the tongue demonstrated gram-positive cocci, gram-negative bacilli, and diplococci. Culture of sputum showed methicillin-resistant Staphylococcus aureus. Inspection for acid-fast bacilli in sputum yielded negative results 3 times. A purified protein derivative skin test for Mycobacterium tuberculosis infection was negative.

Imaging and Other Studies
Computed tomography of the chest and abdomen demonstrated 2 nodular opacities on the lower right lung; spotted opacities on the upper right lung; floccular opacities on the rest area of the lung; mild pleural effusion; enlargement of lymph nodes on the mediastinum, the bilateral hilum of the lung, and mesentery; and hepatosplenomegaly. Electrocardiography showed sinus tachycardia. Nasal cavity endoscopy showed sinusitis. Fundus examination showed vasculopathy of the left retina. A colonoscopy showed normal mucosa.

Histopathology
Biopsy of the nodule on the left arm showed dense, superficial to deep perivascular, periadnexal, perineural, and panniculitislike lymphoid infiltrates, as well as a sparse interstitial infiltrate with irregular and pleomorphic medium to large nuclei. Lymphoid cells showed mild epidermotropism, with tagging to the basal layer. Some vessel walls were infiltrated by similar cells (Figure 2). Infiltrative atypical lymphoid cells expressed CD3 and CD7 and were mostly CD8⁺, with a few CD4⁺ cells and most cells negative for CD5, CD20, CD30, CD56, and anaplastic lymphoma kinase. Cytotoxic markers granzyme B and T-cell intracellular antigen protein 1 were scattered positive. Immunostaining for Ki-67 protein highlighted an increased proliferative rate of 80% in malignant cells. In situ hybridization for EBV-encoded RNA (EBER) demonstrated EBV-positive atypical lymphoid cells (Figure 3). Analysis for T-cell receptor (TCR) γ gene rearrangement revealed a monoclonal pattern. Bone marrow aspirate showed proliferation of the 3 cell lines. The percentage of T lymphocytes was increased (20% of all nucleated cells). No hemophagocytic activity was found.

Diagnosis
A diagnosis of systemic EBV-positive T-cell lymphoma was made. Before the final diagnosis was made, the patient was treated by rheumatologists with antibiotics, antiviral drugs, nonsteroidal anti-inflammatory drugs, and other symptomatic treatments. Following antibiotic therapy, a sputum culture reverted to normal flora, the coagulation index (ie, prothrombin time, activated partial thromboplastin time) returned to normal, and the D-dimer level decreased to 1.19 mg/L.

The patient’s parents refused to accept chemotherapy for him. Instead, they chose herbal therapy only; 5 months later, they reported that all of his symptoms had resolved; however, the disease suddenly relapsed after another 7 months, with multiple skin nodules and fever. The patient died, even with chemotherapy in another hospital.

 

Comment

Prevalence and Presentation
Epstein-Barr virus is a ubiquitous γ-herpesvirus with tropism for B cells, affecting more than 90% of the adult population worldwide. In addition to infecting B cells, EBV is capable of infecting T and NK cells, leading to various EBV-related lymphoproliferative disorders (LPDs). The frequency and clinical presentation of infection varies based on the type of EBV-infected cells and the state of host immunity.^1-3

Primary infection usually is asymptomatic and occurs early in life; when symptomatic, the disease usually presents as infectious mononucleosis (IM), characterized by polyclonal expansion of infected B cells and subsequent cytotoxic T-cell response. A diagnosis of EBV infection can be made by testing for specific IgM and IgG antibodies against VCA, early antigens, and EBV nuclear antigen proteins.^3,4

Associated LPDs
Although most symptoms associated with IM resolve within weeks or months, persistent or recurrent IM-like symptoms or even lasting disease occasionally occur, particularly in children and young adults. This complication is known as chronic active EBV infection (CAEBV), frequently associated with EBV-infected T-cell or NK-cell proliferation, especially in East Asian populations.^3,5

Epstein-Barr virus–positive T-cell and NK-cell LPDs of childhood include CAEBV infection of T-cell and NK-cell types and systemic EBV-positive T-cell lymphoma of childhood. The former includes hydroa vacciniforme–like LPD and severe mosquito bite allergy.³

Systemic EBV-Positive T-cell Lymphoma of Childhood
This entity occurs not only in children but also in adolescents and young adults. A fulminant illness characterized by clonal proliferation of EBV-infected cytotoxic T cells, it can develop shortly after primary EBV infection or is linked to CAEBV infection. The disorder is rare and has a racial predilection for Asian (ie, Japanese, Chinese, Korean) populations and indigenous populations of Mexico and Central and South America.^6-8

Complications
Systemic EBV-positive T-cell lymphoma of childhood is often complicated by hemophagocytic syndrome, coagulopathy, sepsis, and multiorgan failure. Other signs and symptoms include high fever, rash, jaundice, diarrhea, pancytopenia, and hepatosplenomegaly. The liver, spleen, lymph nodes, and bone marrow are commonly involved, and the disease can involve skin, the heart, and the lungs.^9,10

Diagnosis
When systemic EBV-positive T-cell lymphoma occurs shortly after IM, serology shows low or absent anti-VCA IgM and positive anti-VCA IgG. Infiltrating T cells usually are small and lack cytologic atypia; however, cases with pleomorphic, medium to large lymphoid cells, irregular nuclei, and frequent mitoses have been described. Hemophagocytosis can be seen in the liver, spleen, and bone marrow.^3,11

The most typical phenotype of systemic EBV-positive T-cell lymphoma is CD2⁺CD3⁺CD8⁺CD20⁻CD56⁻, with expression of the cytotoxic granules known as T-cell intracellular antigen 1 and granzyme B. Rare cases of CD4⁺ and mixed CD4⁺/CD8⁺ phenotypes have been described, usually in the setting of CAEBV infection.^3,12 Neoplastic cells have monoclonally rearranged TCR-γ genes and consistent EBER positivity with in situ hybridization.¹³ A final diagnosis is based on a comprehensive analysis of clinical, morphological, immunohistochemical, and molecular biological aspects.

Clinical Course and Prognosis
Most patients with systemic EBV-positive T-cell lymphoma have an aggressive clinical course with high mortality. In a few cases, patients were reported to respond to a regimen of etoposide and dexamethasone, followed by allogeneic hematopoietic stem cell transplantation.³

In recognition of the aggressive clinical behavior and desire to clearly distinguish systemic EBV-positive T-cell lymphoma from CAEBV infection, the older term systemic EBV-positive T-cell LPD of childhood, which had been introduced in 2008 to the World Health Organization classification, was changed to systemic EBV-positive T-cell lymphoma of childhood in the revised 2016 World Health Organization classification.^6,12 However, Kim et al¹⁴ reported a case with excellent response to corticosteroid administration, suggesting that systemic EBV-positive T-cell lymphoma of childhood may be more heterogeneous in terms of prognosis.

Our patient presented with acute IM-like symptoms, including high fever, tonsillar enlargement, lymphadenopathy, and hepatosplenomegaly, as well as uncommon oral ulcers and skin lesions, including indurated nodules. Histopathologic changes in the skin nodule, proliferation in bone marrow, immunohistochemical phenotype, and positivity of EBER and TCR-γ monoclonal rearrangement were all consistent with systemic EBV-positive T-cell lymphoma of childhood. The patient was positive for VCA IgG and negative for VCA IgM, compatible with systemic EBV-positive T-cell lymphoma of childhood occurring shortly after IM. Neither pancytopenia, hemophagocytic syndrome, nor multiorgan failure occurred during the course.

Differential Diagnosis
It is important to distinguish IM from systemic EBV-positive T-cell lymphoma of childhood and CAEBV infection. Detection of anti–VCA IgM in the early stage, its disappearance during the clinical course, and appearance of anti-EBV–determined nuclear antigen is useful to distinguish IM from the neoplasms, as systemic EBV-positive T-cell lymphoma of childhood is negative for anti-EBV–determined nuclear antigen. Carefully following the clinical course also is important.^3,15

Epstein-Barr virus–associated hemophagocytic lymphohistiocytosis can occur in association with systemic EBV-positive T-cell lymphoma of childhood and might represent a continuum of disease rather than distinct entities.¹⁴ The most useful marker for differentiating EBV-associated hemophagocytic lymphohistiocytosis and systemic EBV-positive T-cell lymphoma of childhood is an abnormal karyotype rather than molecular clonality.¹⁶

Outcome
Mortality risk in EBV-associated T-cell and NK-cell LPD is not primarily dependent on whether the lesion has progressed to lymphoma but instead is related to associated complications.¹⁷

Conclusion

Although systemic EBV-positive T-cell lymphoma of childhood is a rare disorder and has race predilection, dermatologists should be aware due to the aggressive clinical source and poor prognosis. Histopathology and in situ hybridization for EBER and TCR gene rearrangements are critical for final diagnosis. Although rare cases can show temporary resolution, the final outcome of this disease is not optimistic.

 

Case Report

A 7-year-old Chinese boy presented with multiple painful oral and tongue ulcers of 2 weeks’ duration as well as acute onset of moderate to high fever (highest temperature, 39.3°C) for 5 days. The fever was reported to have run a relapsing course, accompanied by rigors but without convulsions or cognitive changes. At times, the patient had nasal congestion, nasal discharge, and cough. He also had a transient eruption on the back and hands as well as an indurated red nodule on the left forearm.

Before the patient was hospitalized, antibiotic therapy was administered by other physicians, but the condition of fever and oral ulcers did not improve. After the patient was hospitalized, new tender nodules emerged on the scalp, buttocks, and lower extremities. New ulcers also appeared on the palate.

History
Two months earlier, the patient had presented with a painful perioral skin ulcer that resolved after being treated as contagious eczema. Another dermatologist previously had considered a diagnosis of hand-foot-and-mouth disease.

The patient was born by normal spontaneous vaginal delivery, without abnormality. He was breastfed; feeding, growth, and the developmental history showed no abnormality. He was the family’s eldest child, with a healthy brother and sister. There was no history of familial illness. He received bacillus Calmette-Guérin and poliomyelitis vaccines after birth; the rest of the vaccine history was unclear. There was no history of immunologic abnormality.

Physical Examination
A 1.5×1.5-cm, warm, red nodule with a central black crust was noted on the left forearm (Figure 1A). Several similar lesions were noted on the buttocks, scalp, and lower extremities. Multiple ulcers, as large as 1 cm, were present on the tongue, palate, and left angle of the mouth (Figure 1B). The pharynx was congested, and the tonsils were mildly enlarged. Multiple enlarged, movable, nontender lymph nodes could be palpated in the cervical basins, axillae, and groin. No purpura or ecchymosis was detected.

 

 

Laboratory Results
Laboratory testing revealed a normal total white blood cell count (4.26×10⁹/L [reference range, 4.0–12.0×10⁹/L]), with normal neutrophils (1.36×10⁹/L [reference range, 1.32–7.90×10⁹/L]), lymphocytes (2.77×10⁹/L [reference range, 1.20–6.00×10⁹/L]), and monocytes (0.13×10⁹/L [reference range, 0.08–0.80×10⁹/L]); a mildly decreased hemoglobin level (115 g/L [reference range, 120–160 g/L]); a normal platelet count (102×10⁹/L [reference range, 100–380×10⁹/L]); an elevated lactate dehydrogenase level (614 U/L [reference range, 110–330 U/L]); an elevated α-hydroxybutyrate dehydrogenase level (483 U/L [reference range, 120–270 U/L]); elevated prothrombin time (15.3 s [reference range, 9–14 s]); elevated activated partial thromboplastin time (59.8 s [reference range, 20.6–39.6 s]); and an elevated D-dimer level (1.51 mg/L [reference range, <0.73 mg/L]). In addition, autoantibody testing revealed a positive antinuclear antibody titer of 1:320 and a strong positive anti–Ro-52 level.

The peripheral blood lymphocyte classification demonstrated a prominent elevated percentage of T lymphocytes, with predominantly CD8⁺ cells (CD3, 94.87%; CD8, 71.57%; CD4, 24.98%; CD4:CD8 ratio, 0.35) and a diminished percentage of B lymphocytes and natural killer (NK) cells. Epstein-Barr virus (EBV) antibody testing was positive for anti–viral capsid antigen (VCA) IgG and negative for anti-VCA IgM.

Smears of the ulcer on the tongue demonstrated gram-positive cocci, gram-negative bacilli, and diplococci. Culture of sputum showed methicillin-resistant Staphylococcus aureus. Inspection for acid-fast bacilli in sputum yielded negative results 3 times. A purified protein derivative skin test for Mycobacterium tuberculosis infection was negative.

Imaging and Other Studies
Computed tomography of the chest and abdomen demonstrated 2 nodular opacities on the lower right lung; spotted opacities on the upper right lung; floccular opacities on the rest area of the lung; mild pleural effusion; enlargement of lymph nodes on the mediastinum, the bilateral hilum of the lung, and mesentery; and hepatosplenomegaly. Electrocardiography showed sinus tachycardia. Nasal cavity endoscopy showed sinusitis. Fundus examination showed vasculopathy of the left retina. A colonoscopy showed normal mucosa.

Histopathology
Biopsy of the nodule on the left arm showed dense, superficial to deep perivascular, periadnexal, perineural, and panniculitislike lymphoid infiltrates, as well as a sparse interstitial infiltrate with irregular and pleomorphic medium to large nuclei. Lymphoid cells showed mild epidermotropism, with tagging to the basal layer. Some vessel walls were infiltrated by similar cells (Figure 2). Infiltrative atypical lymphoid cells expressed CD3 and CD7 and were mostly CD8⁺, with a few CD4⁺ cells and most cells negative for CD5, CD20, CD30, CD56, and anaplastic lymphoma kinase. Cytotoxic markers granzyme B and T-cell intracellular antigen protein 1 were scattered positive. Immunostaining for Ki-67 protein highlighted an increased proliferative rate of 80% in malignant cells. In situ hybridization for EBV-encoded RNA (EBER) demonstrated EBV-positive atypical lymphoid cells (Figure 3). Analysis for T-cell receptor (TCR) γ gene rearrangement revealed a monoclonal pattern. Bone marrow aspirate showed proliferation of the 3 cell lines. The percentage of T lymphocytes was increased (20% of all nucleated cells). No hemophagocytic activity was found.

Diagnosis
A diagnosis of systemic EBV-positive T-cell lymphoma was made. Before the final diagnosis was made, the patient was treated by rheumatologists with antibiotics, antiviral drugs, nonsteroidal anti-inflammatory drugs, and other symptomatic treatments. Following antibiotic therapy, a sputum culture reverted to normal flora, the coagulation index (ie, prothrombin time, activated partial thromboplastin time) returned to normal, and the D-dimer level decreased to 1.19 mg/L.

The patient’s parents refused to accept chemotherapy for him. Instead, they chose herbal therapy only; 5 months later, they reported that all of his symptoms had resolved; however, the disease suddenly relapsed after another 7 months, with multiple skin nodules and fever. The patient died, even with chemotherapy in another hospital.

 

Comment

Prevalence and Presentation
Epstein-Barr virus is a ubiquitous γ-herpesvirus with tropism for B cells, affecting more than 90% of the adult population worldwide. In addition to infecting B cells, EBV is capable of infecting T and NK cells, leading to various EBV-related lymphoproliferative disorders (LPDs). The frequency and clinical presentation of infection varies based on the type of EBV-infected cells and the state of host immunity.^1-3

Primary infection usually is asymptomatic and occurs early in life; when symptomatic, the disease usually presents as infectious mononucleosis (IM), characterized by polyclonal expansion of infected B cells and subsequent cytotoxic T-cell response. A diagnosis of EBV infection can be made by testing for specific IgM and IgG antibodies against VCA, early antigens, and EBV nuclear antigen proteins.^3,4

Associated LPDs
Although most symptoms associated with IM resolve within weeks or months, persistent or recurrent IM-like symptoms or even lasting disease occasionally occur, particularly in children and young adults. This complication is known as chronic active EBV infection (CAEBV), frequently associated with EBV-infected T-cell or NK-cell proliferation, especially in East Asian populations.^3,5

Epstein-Barr virus–positive T-cell and NK-cell LPDs of childhood include CAEBV infection of T-cell and NK-cell types and systemic EBV-positive T-cell lymphoma of childhood. The former includes hydroa vacciniforme–like LPD and severe mosquito bite allergy.³

Systemic EBV-Positive T-cell Lymphoma of Childhood
This entity occurs not only in children but also in adolescents and young adults. A fulminant illness characterized by clonal proliferation of EBV-infected cytotoxic T cells, it can develop shortly after primary EBV infection or is linked to CAEBV infection. The disorder is rare and has a racial predilection for Asian (ie, Japanese, Chinese, Korean) populations and indigenous populations of Mexico and Central and South America.^6-8

Complications
Systemic EBV-positive T-cell lymphoma of childhood is often complicated by hemophagocytic syndrome, coagulopathy, sepsis, and multiorgan failure. Other signs and symptoms include high fever, rash, jaundice, diarrhea, pancytopenia, and hepatosplenomegaly. The liver, spleen, lymph nodes, and bone marrow are commonly involved, and the disease can involve skin, the heart, and the lungs.^9,10

Diagnosis
When systemic EBV-positive T-cell lymphoma occurs shortly after IM, serology shows low or absent anti-VCA IgM and positive anti-VCA IgG. Infiltrating T cells usually are small and lack cytologic atypia; however, cases with pleomorphic, medium to large lymphoid cells, irregular nuclei, and frequent mitoses have been described. Hemophagocytosis can be seen in the liver, spleen, and bone marrow.^3,11

The most typical phenotype of systemic EBV-positive T-cell lymphoma is CD2⁺CD3⁺CD8⁺CD20⁻CD56⁻, with expression of the cytotoxic granules known as T-cell intracellular antigen 1 and granzyme B. Rare cases of CD4⁺ and mixed CD4⁺/CD8⁺ phenotypes have been described, usually in the setting of CAEBV infection.^3,12 Neoplastic cells have monoclonally rearranged TCR-γ genes and consistent EBER positivity with in situ hybridization.¹³ A final diagnosis is based on a comprehensive analysis of clinical, morphological, immunohistochemical, and molecular biological aspects.

Clinical Course and Prognosis
Most patients with systemic EBV-positive T-cell lymphoma have an aggressive clinical course with high mortality. In a few cases, patients were reported to respond to a regimen of etoposide and dexamethasone, followed by allogeneic hematopoietic stem cell transplantation.³

In recognition of the aggressive clinical behavior and desire to clearly distinguish systemic EBV-positive T-cell lymphoma from CAEBV infection, the older term systemic EBV-positive T-cell LPD of childhood, which had been introduced in 2008 to the World Health Organization classification, was changed to systemic EBV-positive T-cell lymphoma of childhood in the revised 2016 World Health Organization classification.^6,12 However, Kim et al¹⁴ reported a case with excellent response to corticosteroid administration, suggesting that systemic EBV-positive T-cell lymphoma of childhood may be more heterogeneous in terms of prognosis.

Our patient presented with acute IM-like symptoms, including high fever, tonsillar enlargement, lymphadenopathy, and hepatosplenomegaly, as well as uncommon oral ulcers and skin lesions, including indurated nodules. Histopathologic changes in the skin nodule, proliferation in bone marrow, immunohistochemical phenotype, and positivity of EBER and TCR-γ monoclonal rearrangement were all consistent with systemic EBV-positive T-cell lymphoma of childhood. The patient was positive for VCA IgG and negative for VCA IgM, compatible with systemic EBV-positive T-cell lymphoma of childhood occurring shortly after IM. Neither pancytopenia, hemophagocytic syndrome, nor multiorgan failure occurred during the course.

Differential Diagnosis
It is important to distinguish IM from systemic EBV-positive T-cell lymphoma of childhood and CAEBV infection. Detection of anti–VCA IgM in the early stage, its disappearance during the clinical course, and appearance of anti-EBV–determined nuclear antigen is useful to distinguish IM from the neoplasms, as systemic EBV-positive T-cell lymphoma of childhood is negative for anti-EBV–determined nuclear antigen. Carefully following the clinical course also is important.^3,15

Epstein-Barr virus–associated hemophagocytic lymphohistiocytosis can occur in association with systemic EBV-positive T-cell lymphoma of childhood and might represent a continuum of disease rather than distinct entities.¹⁴ The most useful marker for differentiating EBV-associated hemophagocytic lymphohistiocytosis and systemic EBV-positive T-cell lymphoma of childhood is an abnormal karyotype rather than molecular clonality.¹⁶

Outcome
Mortality risk in EBV-associated T-cell and NK-cell LPD is not primarily dependent on whether the lesion has progressed to lymphoma but instead is related to associated complications.¹⁷

Conclusion

Although systemic EBV-positive T-cell lymphoma of childhood is a rare disorder and has race predilection, dermatologists should be aware due to the aggressive clinical source and poor prognosis. Histopathology and in situ hybridization for EBER and TCR gene rearrangements are critical for final diagnosis. Although rare cases can show temporary resolution, the final outcome of this disease is not optimistic.

 

Case Report

A 7-year-old Chinese boy presented with multiple painful oral and tongue ulcers of 2 weeks’ duration as well as acute onset of moderate to high fever (highest temperature, 39.3°C) for 5 days. The fever was reported to have run a relapsing course, accompanied by rigors but without convulsions or cognitive changes. At times, the patient had nasal congestion, nasal discharge, and cough. He also had a transient eruption on the back and hands as well as an indurated red nodule on the left forearm.

Before the patient was hospitalized, antibiotic therapy was administered by other physicians, but the condition of fever and oral ulcers did not improve. After the patient was hospitalized, new tender nodules emerged on the scalp, buttocks, and lower extremities. New ulcers also appeared on the palate.

History
Two months earlier, the patient had presented with a painful perioral skin ulcer that resolved after being treated as contagious eczema. Another dermatologist previously had considered a diagnosis of hand-foot-and-mouth disease.

The patient was born by normal spontaneous vaginal delivery, without abnormality. He was breastfed; feeding, growth, and the developmental history showed no abnormality. He was the family’s eldest child, with a healthy brother and sister. There was no history of familial illness. He received bacillus Calmette-Guérin and poliomyelitis vaccines after birth; the rest of the vaccine history was unclear. There was no history of immunologic abnormality.

Physical Examination
A 1.5×1.5-cm, warm, red nodule with a central black crust was noted on the left forearm (Figure 1A). Several similar lesions were noted on the buttocks, scalp, and lower extremities. Multiple ulcers, as large as 1 cm, were present on the tongue, palate, and left angle of the mouth (Figure 1B). The pharynx was congested, and the tonsils were mildly enlarged. Multiple enlarged, movable, nontender lymph nodes could be palpated in the cervical basins, axillae, and groin. No purpura or ecchymosis was detected.

 

 

Laboratory Results
Laboratory testing revealed a normal total white blood cell count (4.26×10⁹/L [reference range, 4.0–12.0×10⁹/L]), with normal neutrophils (1.36×10⁹/L [reference range, 1.32–7.90×10⁹/L]), lymphocytes (2.77×10⁹/L [reference range, 1.20–6.00×10⁹/L]), and monocytes (0.13×10⁹/L [reference range, 0.08–0.80×10⁹/L]); a mildly decreased hemoglobin level (115 g/L [reference range, 120–160 g/L]); a normal platelet count (102×10⁹/L [reference range, 100–380×10⁹/L]); an elevated lactate dehydrogenase level (614 U/L [reference range, 110–330 U/L]); an elevated α-hydroxybutyrate dehydrogenase level (483 U/L [reference range, 120–270 U/L]); elevated prothrombin time (15.3 s [reference range, 9–14 s]); elevated activated partial thromboplastin time (59.8 s [reference range, 20.6–39.6 s]); and an elevated D-dimer level (1.51 mg/L [reference range, <0.73 mg/L]). In addition, autoantibody testing revealed a positive antinuclear antibody titer of 1:320 and a strong positive anti–Ro-52 level.

The peripheral blood lymphocyte classification demonstrated a prominent elevated percentage of T lymphocytes, with predominantly CD8⁺ cells (CD3, 94.87%; CD8, 71.57%; CD4, 24.98%; CD4:CD8 ratio, 0.35) and a diminished percentage of B lymphocytes and natural killer (NK) cells. Epstein-Barr virus (EBV) antibody testing was positive for anti–viral capsid antigen (VCA) IgG and negative for anti-VCA IgM.

Smears of the ulcer on the tongue demonstrated gram-positive cocci, gram-negative bacilli, and diplococci. Culture of sputum showed methicillin-resistant Staphylococcus aureus. Inspection for acid-fast bacilli in sputum yielded negative results 3 times. A purified protein derivative skin test for Mycobacterium tuberculosis infection was negative.

Imaging and Other Studies
Computed tomography of the chest and abdomen demonstrated 2 nodular opacities on the lower right lung; spotted opacities on the upper right lung; floccular opacities on the rest area of the lung; mild pleural effusion; enlargement of lymph nodes on the mediastinum, the bilateral hilum of the lung, and mesentery; and hepatosplenomegaly. Electrocardiography showed sinus tachycardia. Nasal cavity endoscopy showed sinusitis. Fundus examination showed vasculopathy of the left retina. A colonoscopy showed normal mucosa.

Histopathology
Biopsy of the nodule on the left arm showed dense, superficial to deep perivascular, periadnexal, perineural, and panniculitislike lymphoid infiltrates, as well as a sparse interstitial infiltrate with irregular and pleomorphic medium to large nuclei. Lymphoid cells showed mild epidermotropism, with tagging to the basal layer. Some vessel walls were infiltrated by similar cells (Figure 2). Infiltrative atypical lymphoid cells expressed CD3 and CD7 and were mostly CD8⁺, with a few CD4⁺ cells and most cells negative for CD5, CD20, CD30, CD56, and anaplastic lymphoma kinase. Cytotoxic markers granzyme B and T-cell intracellular antigen protein 1 were scattered positive. Immunostaining for Ki-67 protein highlighted an increased proliferative rate of 80% in malignant cells. In situ hybridization for EBV-encoded RNA (EBER) demonstrated EBV-positive atypical lymphoid cells (Figure 3). Analysis for T-cell receptor (TCR) γ gene rearrangement revealed a monoclonal pattern. Bone marrow aspirate showed proliferation of the 3 cell lines. The percentage of T lymphocytes was increased (20% of all nucleated cells). No hemophagocytic activity was found.

Diagnosis
A diagnosis of systemic EBV-positive T-cell lymphoma was made. Before the final diagnosis was made, the patient was treated by rheumatologists with antibiotics, antiviral drugs, nonsteroidal anti-inflammatory drugs, and other symptomatic treatments. Following antibiotic therapy, a sputum culture reverted to normal flora, the coagulation index (ie, prothrombin time, activated partial thromboplastin time) returned to normal, and the D-dimer level decreased to 1.19 mg/L.

The patient’s parents refused to accept chemotherapy for him. Instead, they chose herbal therapy only; 5 months later, they reported that all of his symptoms had resolved; however, the disease suddenly relapsed after another 7 months, with multiple skin nodules and fever. The patient died, even with chemotherapy in another hospital.

 

Comment

Prevalence and Presentation
Epstein-Barr virus is a ubiquitous γ-herpesvirus with tropism for B cells, affecting more than 90% of the adult population worldwide. In addition to infecting B cells, EBV is capable of infecting T and NK cells, leading to various EBV-related lymphoproliferative disorders (LPDs). The frequency and clinical presentation of infection varies based on the type of EBV-infected cells and the state of host immunity.^1-3

Primary infection usually is asymptomatic and occurs early in life; when symptomatic, the disease usually presents as infectious mononucleosis (IM), characterized by polyclonal expansion of infected B cells and subsequent cytotoxic T-cell response. A diagnosis of EBV infection can be made by testing for specific IgM and IgG antibodies against VCA, early antigens, and EBV nuclear antigen proteins.^3,4

Associated LPDs
Although most symptoms associated with IM resolve within weeks or months, persistent or recurrent IM-like symptoms or even lasting disease occasionally occur, particularly in children and young adults. This complication is known as chronic active EBV infection (CAEBV), frequently associated with EBV-infected T-cell or NK-cell proliferation, especially in East Asian populations.^3,5

Epstein-Barr virus–positive T-cell and NK-cell LPDs of childhood include CAEBV infection of T-cell and NK-cell types and systemic EBV-positive T-cell lymphoma of childhood. The former includes hydroa vacciniforme–like LPD and severe mosquito bite allergy.³

Systemic EBV-Positive T-cell Lymphoma of Childhood
This entity occurs not only in children but also in adolescents and young adults. A fulminant illness characterized by clonal proliferation of EBV-infected cytotoxic T cells, it can develop shortly after primary EBV infection or is linked to CAEBV infection. The disorder is rare and has a racial predilection for Asian (ie, Japanese, Chinese, Korean) populations and indigenous populations of Mexico and Central and South America.^6-8

Complications
Systemic EBV-positive T-cell lymphoma of childhood is often complicated by hemophagocytic syndrome, coagulopathy, sepsis, and multiorgan failure. Other signs and symptoms include high fever, rash, jaundice, diarrhea, pancytopenia, and hepatosplenomegaly. The liver, spleen, lymph nodes, and bone marrow are commonly involved, and the disease can involve skin, the heart, and the lungs.^9,10

Diagnosis
When systemic EBV-positive T-cell lymphoma occurs shortly after IM, serology shows low or absent anti-VCA IgM and positive anti-VCA IgG. Infiltrating T cells usually are small and lack cytologic atypia; however, cases with pleomorphic, medium to large lymphoid cells, irregular nuclei, and frequent mitoses have been described. Hemophagocytosis can be seen in the liver, spleen, and bone marrow.^3,11

The most typical phenotype of systemic EBV-positive T-cell lymphoma is CD2⁺CD3⁺CD8⁺CD20⁻CD56⁻, with expression of the cytotoxic granules known as T-cell intracellular antigen 1 and granzyme B. Rare cases of CD4⁺ and mixed CD4⁺/CD8⁺ phenotypes have been described, usually in the setting of CAEBV infection.^3,12 Neoplastic cells have monoclonally rearranged TCR-γ genes and consistent EBER positivity with in situ hybridization.¹³ A final diagnosis is based on a comprehensive analysis of clinical, morphological, immunohistochemical, and molecular biological aspects.

Clinical Course and Prognosis
Most patients with systemic EBV-positive T-cell lymphoma have an aggressive clinical course with high mortality. In a few cases, patients were reported to respond to a regimen of etoposide and dexamethasone, followed by allogeneic hematopoietic stem cell transplantation.³

In recognition of the aggressive clinical behavior and desire to clearly distinguish systemic EBV-positive T-cell lymphoma from CAEBV infection, the older term systemic EBV-positive T-cell LPD of childhood, which had been introduced in 2008 to the World Health Organization classification, was changed to systemic EBV-positive T-cell lymphoma of childhood in the revised 2016 World Health Organization classification.^6,12 However, Kim et al¹⁴ reported a case with excellent response to corticosteroid administration, suggesting that systemic EBV-positive T-cell lymphoma of childhood may be more heterogeneous in terms of prognosis.

Our patient presented with acute IM-like symptoms, including high fever, tonsillar enlargement, lymphadenopathy, and hepatosplenomegaly, as well as uncommon oral ulcers and skin lesions, including indurated nodules. Histopathologic changes in the skin nodule, proliferation in bone marrow, immunohistochemical phenotype, and positivity of EBER and TCR-γ monoclonal rearrangement were all consistent with systemic EBV-positive T-cell lymphoma of childhood. The patient was positive for VCA IgG and negative for VCA IgM, compatible with systemic EBV-positive T-cell lymphoma of childhood occurring shortly after IM. Neither pancytopenia, hemophagocytic syndrome, nor multiorgan failure occurred during the course.

Differential Diagnosis
It is important to distinguish IM from systemic EBV-positive T-cell lymphoma of childhood and CAEBV infection. Detection of anti–VCA IgM in the early stage, its disappearance during the clinical course, and appearance of anti-EBV–determined nuclear antigen is useful to distinguish IM from the neoplasms, as systemic EBV-positive T-cell lymphoma of childhood is negative for anti-EBV–determined nuclear antigen. Carefully following the clinical course also is important.^3,15

Epstein-Barr virus–associated hemophagocytic lymphohistiocytosis can occur in association with systemic EBV-positive T-cell lymphoma of childhood and might represent a continuum of disease rather than distinct entities.¹⁴ The most useful marker for differentiating EBV-associated hemophagocytic lymphohistiocytosis and systemic EBV-positive T-cell lymphoma of childhood is an abnormal karyotype rather than molecular clonality.¹⁶

Outcome
Mortality risk in EBV-associated T-cell and NK-cell LPD is not primarily dependent on whether the lesion has progressed to lymphoma but instead is related to associated complications.¹⁷

Conclusion

Although systemic EBV-positive T-cell lymphoma of childhood is a rare disorder and has race predilection, dermatologists should be aware due to the aggressive clinical source and poor prognosis. Histopathology and in situ hybridization for EBER and TCR gene rearrangements are critical for final diagnosis. Although rare cases can show temporary resolution, the final outcome of this disease is not optimistic.

The Diagnosis: Inflammatory Urothelial Carcinoma 

Microscopic examination revealed metastatic carcinoma with extensive dermal lymphatic invasion (Figure). Immunohistochemical stains were positive for p63 and GATA3, markers for urothelial carcinomas, and negative for S-100 and Melan-A, markers for melanoma. Thus, the biopsy was compatible with a diagnosis of urothelial carcinoma. Gram and Grocott-Gomori methenamine-silver stains were negative for bacterial or fungal organisms. An additional 4-mm punch biopsy was performed of the left thigh at the distal-most aspect of the eruption to determine the extent of cutaneous metastasis. Pathology again showed metastatic urothelial carcinoma with extensive dermal lymphatic involvement and overlying epidermal spongiosis.

 

The patient had a history of bladder cancer diagnosed 1.5 years prior to presentation. It was a high-grade (World Health Organization) urothelial carcinoma that penetrated the bladder muscular wall, focally infiltrating into pericystic fat with multifocal seeding of pericystic lymphatics. It was unresponsive to bacillus Calmette-Guérin therapy. He underwent a cystoprostatectomy and bilateral staging lymph node dissection with clear surgical margins without adjuvant chemotherapy or radiation. He also reported a history of 2 prior cutaneous melanomas that were excised without sentinel lymph node biopsy. 

Four months prior to presentation, he developed a mildly pruritic cutaneous eruption on the abdomen that was treated with topical miconazole for presumed tinea cruris without improvement. He also was previously diagnosed with candidiasis of his urostomy and was taking oral fluconazole. The patient was admitted for the abdominal pain and distension, and computed tomography of the abdomen and pelvis revealed peritoneal carcinomatosis resulting in mechanical small bowel obstruction as well as enlarged pelvic and retroperitoneal lymph nodes. Confirmation of metastatic disease via skin biopsy avoided an invasive peritoneal biopsy. He was treated with triamcinolone acetonide ointment 0.1% with moderate relief of pruritus, and a palliative percutaneous endoscopic gastrostomy tube was placed for bowel decompression. The patient's hospital course was complicated by Proteus mirabilis bacteremia requiring cefepime. He was transitioned to home hospice and died 1 month after presentation. 

Inflammatory carcinoma, also called carcinoma erysipeloides, is a type of cutaneous metastasis most commonly seen in breast adenocarcinoma. Reported cases secondary to urothelial carcinoma are rare and most often involve the abdomen, groin, and lower extremities.^1-5 Clinically, inflammatory carcinoma presents as erythematous indurated patches or plaques with well-defined borders, often with edema, warmth, and tenderness. Its morphologic appearance is due to the obstruction of lymphatic vessels by tumor cells and the release of inflammatory cytokines. Its presentation can mimic other dermatoses such as cellulitis, erysipelas, fungal infection, radiation dermatitis, Majocchi granuloma, or contact dermatitis.⁶ Cutaneous metastases may be the first clinical manifestations of metastatic disease, and they may occur due to hematogenous and lymphatic spread, direct contiguous tissue invasion, or iatrogenic implantation following surgical excision of the primary tumor. Histologically, nuclear markers GATA3 and p63 stain positively in urothelial carcinomas and are negative in prostatic adenocarcinomas.^7,8 Other markers may be used such as cytokeratins 7 and 20, which are cytoplasmic epithelial markers that both stain positive in urothelial neoplasms.⁹  

Inflammatory carcinoma may be treated with radiation or systemic chemotherapy depending on the extent of systemic involvement in the patient; however, its presence portends a poor prognosis. Less than 1% of genitourinary malignancies have cutaneous involvement, and median disease-specific survival is less than 6 months from presentation of the cutaneous metastasis.¹⁰ Clinicians faced with a recalcitrant inflammatory cutaneous eruption should maintain a high index of suspicion for cutaneous metastases, particularly in patients with a history of cancer. Early dermatology referral may help establish the diagnosis and guide disease-targeted therapy or goals of care discussions. 

The Diagnosis: Inflammatory Urothelial Carcinoma 

Microscopic examination revealed metastatic carcinoma with extensive dermal lymphatic invasion (Figure). Immunohistochemical stains were positive for p63 and GATA3, markers for urothelial carcinomas, and negative for S-100 and Melan-A, markers for melanoma. Thus, the biopsy was compatible with a diagnosis of urothelial carcinoma. Gram and Grocott-Gomori methenamine-silver stains were negative for bacterial or fungal organisms. An additional 4-mm punch biopsy was performed of the left thigh at the distal-most aspect of the eruption to determine the extent of cutaneous metastasis. Pathology again showed metastatic urothelial carcinoma with extensive dermal lymphatic involvement and overlying epidermal spongiosis.

 

The patient had a history of bladder cancer diagnosed 1.5 years prior to presentation. It was a high-grade (World Health Organization) urothelial carcinoma that penetrated the bladder muscular wall, focally infiltrating into pericystic fat with multifocal seeding of pericystic lymphatics. It was unresponsive to bacillus Calmette-Guérin therapy. He underwent a cystoprostatectomy and bilateral staging lymph node dissection with clear surgical margins without adjuvant chemotherapy or radiation. He also reported a history of 2 prior cutaneous melanomas that were excised without sentinel lymph node biopsy. 

Four months prior to presentation, he developed a mildly pruritic cutaneous eruption on the abdomen that was treated with topical miconazole for presumed tinea cruris without improvement. He also was previously diagnosed with candidiasis of his urostomy and was taking oral fluconazole. The patient was admitted for the abdominal pain and distension, and computed tomography of the abdomen and pelvis revealed peritoneal carcinomatosis resulting in mechanical small bowel obstruction as well as enlarged pelvic and retroperitoneal lymph nodes. Confirmation of metastatic disease via skin biopsy avoided an invasive peritoneal biopsy. He was treated with triamcinolone acetonide ointment 0.1% with moderate relief of pruritus, and a palliative percutaneous endoscopic gastrostomy tube was placed for bowel decompression. The patient's hospital course was complicated by Proteus mirabilis bacteremia requiring cefepime. He was transitioned to home hospice and died 1 month after presentation. 

Inflammatory carcinoma, also called carcinoma erysipeloides, is a type of cutaneous metastasis most commonly seen in breast adenocarcinoma. Reported cases secondary to urothelial carcinoma are rare and most often involve the abdomen, groin, and lower extremities.^1-5 Clinically, inflammatory carcinoma presents as erythematous indurated patches or plaques with well-defined borders, often with edema, warmth, and tenderness. Its morphologic appearance is due to the obstruction of lymphatic vessels by tumor cells and the release of inflammatory cytokines. Its presentation can mimic other dermatoses such as cellulitis, erysipelas, fungal infection, radiation dermatitis, Majocchi granuloma, or contact dermatitis.⁶ Cutaneous metastases may be the first clinical manifestations of metastatic disease, and they may occur due to hematogenous and lymphatic spread, direct contiguous tissue invasion, or iatrogenic implantation following surgical excision of the primary tumor. Histologically, nuclear markers GATA3 and p63 stain positively in urothelial carcinomas and are negative in prostatic adenocarcinomas.^7,8 Other markers may be used such as cytokeratins 7 and 20, which are cytoplasmic epithelial markers that both stain positive in urothelial neoplasms.⁹  

Inflammatory carcinoma may be treated with radiation or systemic chemotherapy depending on the extent of systemic involvement in the patient; however, its presence portends a poor prognosis. Less than 1% of genitourinary malignancies have cutaneous involvement, and median disease-specific survival is less than 6 months from presentation of the cutaneous metastasis.¹⁰ Clinicians faced with a recalcitrant inflammatory cutaneous eruption should maintain a high index of suspicion for cutaneous metastases, particularly in patients with a history of cancer. Early dermatology referral may help establish the diagnosis and guide disease-targeted therapy or goals of care discussions. 

The Diagnosis: Inflammatory Urothelial Carcinoma 

Microscopic examination revealed metastatic carcinoma with extensive dermal lymphatic invasion (Figure). Immunohistochemical stains were positive for p63 and GATA3, markers for urothelial carcinomas, and negative for S-100 and Melan-A, markers for melanoma. Thus, the biopsy was compatible with a diagnosis of urothelial carcinoma. Gram and Grocott-Gomori methenamine-silver stains were negative for bacterial or fungal organisms. An additional 4-mm punch biopsy was performed of the left thigh at the distal-most aspect of the eruption to determine the extent of cutaneous metastasis. Pathology again showed metastatic urothelial carcinoma with extensive dermal lymphatic involvement and overlying epidermal spongiosis.

 

The patient had a history of bladder cancer diagnosed 1.5 years prior to presentation. It was a high-grade (World Health Organization) urothelial carcinoma that penetrated the bladder muscular wall, focally infiltrating into pericystic fat with multifocal seeding of pericystic lymphatics. It was unresponsive to bacillus Calmette-Guérin therapy. He underwent a cystoprostatectomy and bilateral staging lymph node dissection with clear surgical margins without adjuvant chemotherapy or radiation. He also reported a history of 2 prior cutaneous melanomas that were excised without sentinel lymph node biopsy. 

Four months prior to presentation, he developed a mildly pruritic cutaneous eruption on the abdomen that was treated with topical miconazole for presumed tinea cruris without improvement. He also was previously diagnosed with candidiasis of his urostomy and was taking oral fluconazole. The patient was admitted for the abdominal pain and distension, and computed tomography of the abdomen and pelvis revealed peritoneal carcinomatosis resulting in mechanical small bowel obstruction as well as enlarged pelvic and retroperitoneal lymph nodes. Confirmation of metastatic disease via skin biopsy avoided an invasive peritoneal biopsy. He was treated with triamcinolone acetonide ointment 0.1% with moderate relief of pruritus, and a palliative percutaneous endoscopic gastrostomy tube was placed for bowel decompression. The patient's hospital course was complicated by Proteus mirabilis bacteremia requiring cefepime. He was transitioned to home hospice and died 1 month after presentation. 

Inflammatory carcinoma, also called carcinoma erysipeloides, is a type of cutaneous metastasis most commonly seen in breast adenocarcinoma. Reported cases secondary to urothelial carcinoma are rare and most often involve the abdomen, groin, and lower extremities.^1-5 Clinically, inflammatory carcinoma presents as erythematous indurated patches or plaques with well-defined borders, often with edema, warmth, and tenderness. Its morphologic appearance is due to the obstruction of lymphatic vessels by tumor cells and the release of inflammatory cytokines. Its presentation can mimic other dermatoses such as cellulitis, erysipelas, fungal infection, radiation dermatitis, Majocchi granuloma, or contact dermatitis.⁶ Cutaneous metastases may be the first clinical manifestations of metastatic disease, and they may occur due to hematogenous and lymphatic spread, direct contiguous tissue invasion, or iatrogenic implantation following surgical excision of the primary tumor. Histologically, nuclear markers GATA3 and p63 stain positively in urothelial carcinomas and are negative in prostatic adenocarcinomas.^7,8 Other markers may be used such as cytokeratins 7 and 20, which are cytoplasmic epithelial markers that both stain positive in urothelial neoplasms.⁹  

Inflammatory carcinoma may be treated with radiation or systemic chemotherapy depending on the extent of systemic involvement in the patient; however, its presence portends a poor prognosis. Less than 1% of genitourinary malignancies have cutaneous involvement, and median disease-specific survival is less than 6 months from presentation of the cutaneous metastasis.¹⁰ Clinicians faced with a recalcitrant inflammatory cutaneous eruption should maintain a high index of suspicion for cutaneous metastases, particularly in patients with a history of cancer. Early dermatology referral may help establish the diagnosis and guide disease-targeted therapy or goals of care discussions. 

The Diagnosis: Lichenoid and Granulomatous Dermatitis in the Setting of Secondary Syphilis  

Syphilis, an infectious disease that has risen in incidence and is most commonly reported in men who have sex with men, involves a vast array of clinical and histologic presentations.¹ Clinically, secondary syphilis involves an erythematous maculopapular eruption on the face, trunk, palms, soles, or genital area.² The characteristic histologic features for secondary syphilis include endothelial swelling, interstitial inflammatory array, irregular acanthosis, elongated rete ridges, and vacuolar interface dermatitis with lymphocytes and plasma cells.¹ Syphilitic infection has been associated with lichenoid and granulomatous dermatitis, which is an inflammatory skin disease described by Magro and Crowson.³ Lichenoid and granulomatous dermatitis has been linked to various systemic disorders, including chronic hepatitis C, Crohn disease, rheumatoid arthritis, endocrinopathy, subacute cutaneous lupus erythematosus, secondary syphilis, prior herpes infection, tuberculoid leprosy, mycobacterial infection, and human immunodeficiency virus infection.^3-7 For this patient, given histopathology findings, clinical presentation, and positive rapid plasma reagin serologies, a diagnosis of lichenoid and granulomatous dermatitis in the setting of a secondary syphilis infection was established. A comprehensive investigation should be conducted to consider secondary syphilis or other systemic diseases in patients with a histologic finding of lichenoid and granulomatous dermatitis. 

Histologically, lichenoid and granulomatous dermatitis cases show a bandlike infiltrate of lymphocytes with neighboring histiocytes along the dermoepidermal junction, accompanied by epithelial changes of dyskeratosis, vasculopathy, and colloid body formation, in addition to a dermal histiocytic component.³ Our patient's biopsy showed a lichenoid reaction pattern with vacuolar interface changes, dyskeratosis, plump endothelial cells, and small collections of plasma cells. Additionally, there was a granulomatous component in the dermis with histiocytes admixed with lymphocytes and plasma cells. The presence of spirochetes was confirmed with antitreponemal immunohistochemical stain (Figure 1). Quantitative rapid plasma reagin was 1:64 (reference range, <1:1) and Treponema pallidum antibody was reactive. 

Interstitial granulomatous dermatitis has a variable clinical presentation, often with red-purple annular plaques, hyperpigmented papules, and nodules frequently in a linear arrangement and predominantly on the trunk, thighs, groin, or buttocks.^8,9 On histopathology, there are histiocytes in the reticular dermis and/or a macrophage infiltrate in the mid to deep dermis with collections of degenerated collagen (Figure 2).^8,10 An interstitial infiltrate of eosinophils and neutrophils also may be appreciated, but mucin generally is absent.^8,11 This condition often coexists with rheumatic and systemic autoimmune diseases.^8-10  

Interstitial granuloma annulare is a noninfectious granulomatous skin condition that often presents clinically as asymptomatic annular red-brown patches, usually on the extremities.^11-13 On histopathology, an interstitial or palisaded inflammatory infiltrate with histiocytes and multinucleated giant cells may be seen along with collagen degeneration or collagen bundles without necrosis (Figure 3).⁹ Mucin often is associated with the histiocytes.¹¹ Of note, our patient's skin biopsy shows interface dermatitis, differentiating it from both interstitial granuloma annulare and interstitial granulomatous dermatitis. 

Postviral granulomatous reactions are the most frequently reported types of reactions to occur at the location of herpes zoster infection up to years after the initial disease. Wolf isotopic reaction encompasses skin reactions in the body region of formerly resolved skin disease, commonly herpesvirus infection.^14,15 This manifestation may occur due to a hypersensitivity reaction from enduring viral proteins, resident memory T cells, or local neuroimmune imbalance from herpesvirus-induced injury to dermal sensory nerve fibers.^14-17 Clinically, patients present with red-purple pruritic papules and plaques in a bandlike unilateral pattern, usually in the same region as the prior herpes infection and often accompanied by postherpetic neuralgia.^16-19 Of note, our patient's clinical findings were more diffuse than the frequently localized and often linear distribution seen in postherpetic granulomatous reaction. On histopathology, granulomatous or lichenoid tissue reaction most commonly is appreciated.¹⁵ Specifically, interstitial granulomatous dermatitis with histiocytes, lymphocytes, and multinucleated giant cells showing elastophagocytosis and an inflammatory infiltrate with lymphocytes and plasma cells around vasculature, eccrine glands, and nerves can be noted (Figure 4).¹⁹  

Lupus erythematosus is an autoimmune condition with a wide array of clinical features, including skin manifestations and systemic symptoms. Specifically, discoid lupus erythematosus presents with clearly outlined, red-pink macules or papules with scaling. Histologic features include keratotic follicular plugging, acanthosis, dermal mucin, thickening of the basement membrane zone, and dense lymphocytic infiltrate (Figure 5).²⁰  

The Diagnosis: Lichenoid and Granulomatous Dermatitis in the Setting of Secondary Syphilis  

Syphilis, an infectious disease that has risen in incidence and is most commonly reported in men who have sex with men, involves a vast array of clinical and histologic presentations.¹ Clinically, secondary syphilis involves an erythematous maculopapular eruption on the face, trunk, palms, soles, or genital area.² The characteristic histologic features for secondary syphilis include endothelial swelling, interstitial inflammatory array, irregular acanthosis, elongated rete ridges, and vacuolar interface dermatitis with lymphocytes and plasma cells.¹ Syphilitic infection has been associated with lichenoid and granulomatous dermatitis, which is an inflammatory skin disease described by Magro and Crowson.³ Lichenoid and granulomatous dermatitis has been linked to various systemic disorders, including chronic hepatitis C, Crohn disease, rheumatoid arthritis, endocrinopathy, subacute cutaneous lupus erythematosus, secondary syphilis, prior herpes infection, tuberculoid leprosy, mycobacterial infection, and human immunodeficiency virus infection.^3-7 For this patient, given histopathology findings, clinical presentation, and positive rapid plasma reagin serologies, a diagnosis of lichenoid and granulomatous dermatitis in the setting of a secondary syphilis infection was established. A comprehensive investigation should be conducted to consider secondary syphilis or other systemic diseases in patients with a histologic finding of lichenoid and granulomatous dermatitis. 

Histologically, lichenoid and granulomatous dermatitis cases show a bandlike infiltrate of lymphocytes with neighboring histiocytes along the dermoepidermal junction, accompanied by epithelial changes of dyskeratosis, vasculopathy, and colloid body formation, in addition to a dermal histiocytic component.³ Our patient's biopsy showed a lichenoid reaction pattern with vacuolar interface changes, dyskeratosis, plump endothelial cells, and small collections of plasma cells. Additionally, there was a granulomatous component in the dermis with histiocytes admixed with lymphocytes and plasma cells. The presence of spirochetes was confirmed with antitreponemal immunohistochemical stain (Figure 1). Quantitative rapid plasma reagin was 1:64 (reference range, <1:1) and Treponema pallidum antibody was reactive. 

Interstitial granulomatous dermatitis has a variable clinical presentation, often with red-purple annular plaques, hyperpigmented papules, and nodules frequently in a linear arrangement and predominantly on the trunk, thighs, groin, or buttocks.^8,9 On histopathology, there are histiocytes in the reticular dermis and/or a macrophage infiltrate in the mid to deep dermis with collections of degenerated collagen (Figure 2).^8,10 An interstitial infiltrate of eosinophils and neutrophils also may be appreciated, but mucin generally is absent.^8,11 This condition often coexists with rheumatic and systemic autoimmune diseases.^8-10  

Interstitial granuloma annulare is a noninfectious granulomatous skin condition that often presents clinically as asymptomatic annular red-brown patches, usually on the extremities.^11-13 On histopathology, an interstitial or palisaded inflammatory infiltrate with histiocytes and multinucleated giant cells may be seen along with collagen degeneration or collagen bundles without necrosis (Figure 3).⁹ Mucin often is associated with the histiocytes.¹¹ Of note, our patient's skin biopsy shows interface dermatitis, differentiating it from both interstitial granuloma annulare and interstitial granulomatous dermatitis. 

Postviral granulomatous reactions are the most frequently reported types of reactions to occur at the location of herpes zoster infection up to years after the initial disease. Wolf isotopic reaction encompasses skin reactions in the body region of formerly resolved skin disease, commonly herpesvirus infection.^14,15 This manifestation may occur due to a hypersensitivity reaction from enduring viral proteins, resident memory T cells, or local neuroimmune imbalance from herpesvirus-induced injury to dermal sensory nerve fibers.^14-17 Clinically, patients present with red-purple pruritic papules and plaques in a bandlike unilateral pattern, usually in the same region as the prior herpes infection and often accompanied by postherpetic neuralgia.^16-19 Of note, our patient's clinical findings were more diffuse than the frequently localized and often linear distribution seen in postherpetic granulomatous reaction. On histopathology, granulomatous or lichenoid tissue reaction most commonly is appreciated.¹⁵ Specifically, interstitial granulomatous dermatitis with histiocytes, lymphocytes, and multinucleated giant cells showing elastophagocytosis and an inflammatory infiltrate with lymphocytes and plasma cells around vasculature, eccrine glands, and nerves can be noted (Figure 4).¹⁹  

Lupus erythematosus is an autoimmune condition with a wide array of clinical features, including skin manifestations and systemic symptoms. Specifically, discoid lupus erythematosus presents with clearly outlined, red-pink macules or papules with scaling. Histologic features include keratotic follicular plugging, acanthosis, dermal mucin, thickening of the basement membrane zone, and dense lymphocytic infiltrate (Figure 5).²⁰  

The Diagnosis: Lichenoid and Granulomatous Dermatitis in the Setting of Secondary Syphilis  

Syphilis, an infectious disease that has risen in incidence and is most commonly reported in men who have sex with men, involves a vast array of clinical and histologic presentations.¹ Clinically, secondary syphilis involves an erythematous maculopapular eruption on the face, trunk, palms, soles, or genital area.² The characteristic histologic features for secondary syphilis include endothelial swelling, interstitial inflammatory array, irregular acanthosis, elongated rete ridges, and vacuolar interface dermatitis with lymphocytes and plasma cells.¹ Syphilitic infection has been associated with lichenoid and granulomatous dermatitis, which is an inflammatory skin disease described by Magro and Crowson.³ Lichenoid and granulomatous dermatitis has been linked to various systemic disorders, including chronic hepatitis C, Crohn disease, rheumatoid arthritis, endocrinopathy, subacute cutaneous lupus erythematosus, secondary syphilis, prior herpes infection, tuberculoid leprosy, mycobacterial infection, and human immunodeficiency virus infection.^3-7 For this patient, given histopathology findings, clinical presentation, and positive rapid plasma reagin serologies, a diagnosis of lichenoid and granulomatous dermatitis in the setting of a secondary syphilis infection was established. A comprehensive investigation should be conducted to consider secondary syphilis or other systemic diseases in patients with a histologic finding of lichenoid and granulomatous dermatitis. 

Histologically, lichenoid and granulomatous dermatitis cases show a bandlike infiltrate of lymphocytes with neighboring histiocytes along the dermoepidermal junction, accompanied by epithelial changes of dyskeratosis, vasculopathy, and colloid body formation, in addition to a dermal histiocytic component.³ Our patient's biopsy showed a lichenoid reaction pattern with vacuolar interface changes, dyskeratosis, plump endothelial cells, and small collections of plasma cells. Additionally, there was a granulomatous component in the dermis with histiocytes admixed with lymphocytes and plasma cells. The presence of spirochetes was confirmed with antitreponemal immunohistochemical stain (Figure 1). Quantitative rapid plasma reagin was 1:64 (reference range, <1:1) and Treponema pallidum antibody was reactive. 

Interstitial granulomatous dermatitis has a variable clinical presentation, often with red-purple annular plaques, hyperpigmented papules, and nodules frequently in a linear arrangement and predominantly on the trunk, thighs, groin, or buttocks.^8,9 On histopathology, there are histiocytes in the reticular dermis and/or a macrophage infiltrate in the mid to deep dermis with collections of degenerated collagen (Figure 2).^8,10 An interstitial infiltrate of eosinophils and neutrophils also may be appreciated, but mucin generally is absent.^8,11 This condition often coexists with rheumatic and systemic autoimmune diseases.^8-10  

Interstitial granuloma annulare is a noninfectious granulomatous skin condition that often presents clinically as asymptomatic annular red-brown patches, usually on the extremities.^11-13 On histopathology, an interstitial or palisaded inflammatory infiltrate with histiocytes and multinucleated giant cells may be seen along with collagen degeneration or collagen bundles without necrosis (Figure 3).⁹ Mucin often is associated with the histiocytes.¹¹ Of note, our patient's skin biopsy shows interface dermatitis, differentiating it from both interstitial granuloma annulare and interstitial granulomatous dermatitis. 

Postviral granulomatous reactions are the most frequently reported types of reactions to occur at the location of herpes zoster infection up to years after the initial disease. Wolf isotopic reaction encompasses skin reactions in the body region of formerly resolved skin disease, commonly herpesvirus infection.^14,15 This manifestation may occur due to a hypersensitivity reaction from enduring viral proteins, resident memory T cells, or local neuroimmune imbalance from herpesvirus-induced injury to dermal sensory nerve fibers.^14-17 Clinically, patients present with red-purple pruritic papules and plaques in a bandlike unilateral pattern, usually in the same region as the prior herpes infection and often accompanied by postherpetic neuralgia.^16-19 Of note, our patient's clinical findings were more diffuse than the frequently localized and often linear distribution seen in postherpetic granulomatous reaction. On histopathology, granulomatous or lichenoid tissue reaction most commonly is appreciated.¹⁵ Specifically, interstitial granulomatous dermatitis with histiocytes, lymphocytes, and multinucleated giant cells showing elastophagocytosis and an inflammatory infiltrate with lymphocytes and plasma cells around vasculature, eccrine glands, and nerves can be noted (Figure 4).¹⁹  

Lupus erythematosus is an autoimmune condition with a wide array of clinical features, including skin manifestations and systemic symptoms. Specifically, discoid lupus erythematosus presents with clearly outlined, red-pink macules or papules with scaling. Histologic features include keratotic follicular plugging, acanthosis, dermal mucin, thickening of the basement membrane zone, and dense lymphocytic infiltrate (Figure 5).²⁰  

The Diagnosis: Cutaneous Sarcoidosis  

Histologic examination of the shave biopsy showed focal parakeratosis, irregular epidermal hyperplasia, and multiple noncaseating naked granulomas with occasional multinucleated giant cells in the dermis (Figure, A). The granulomas were surrounded by mild lymphocytic infiltration with rare eosinophils (Figure, B). Periodic acid-Schiff and Fite stains were negative for organisms, and polariscopic examination was negative; these findings confirmed the diagnosis of cutaneous sarcoidosis. Topical or intralesional steroids were recommended, but our patient declined treatment given that the lesions were asymptomatic.  

Sarcoidosis is a multisystem granulomatous disease of unknown etiology that affects the skin in approximately 25% of patients.¹ Cutaneous lesions manifest in 2 forms: specific and nonspecific. Noncaseating granulomas are considered specific. Nonspecific lesions include erythema nodosum, calcinosis cutis, Sweet syndrome, and nail clubbing. The most common sites of specific sarcoidosis lesions include the face, lips, neck, upper trunk, and extremities. Few cases have reported cutaneous sarcoidosis involving the genitalia; most reports describe vulvar cutaneous sarcoidosis.^2-4 Although there have been reports of sarcoidosis involving the epididymis and testes, which presented as scrotal masses, cutaneous scrotal involvement with the skin as the primary site of involvement is rare.^5,6 McLaughlin et al⁵ reported an extensive, pruritic, and eczematous eruption of the scrotum with associated edema and tenderness. Wei et al⁶ reported cutaneous sarcoidosis in the form of multiple indurated papules involving the penis and scrotum, similar to our case.  

Comparing our patient to the case reported by Wei et al,⁶ both patients had Fitzpatrick skin type V or VI and systemic involvement including pulmonary disease. However, Wei et al⁶ did not clearly mention if the cutaneous manifestations preceded the diagnosis of systemic sarcoidosis or if they were present at the time of the diagnosis. Our patient developed cutaneous lesions 4 years after being diagnosed with systemic sarcoidosis from hilar lymphadenopathy. In addition to the scrotal lesions, he also had a lesion of lupus pernio presenting as a violaceous to brown plaque on the tip of the nose. Although both patients denied pruritus, the other patient's lesions were painful.⁶ Wei et al⁶ mentioned that treatment with topical, intralesional, and systemic steroids failed, and the patient's lesions continued to progress. Generally, topical and intralesional steroids are considered mainstay treatment of cutaneous sarcoidosis despite insufficient data to support their efficacy.⁷  

The differential diagnosis of papules on the scrotum can be broad. Our provisional diagnoses for this particular morphology of small, flesh-colored, shiny, polygonal, flat-topped papules included condyloma acuminatum; lichen planus; idiopathic scrotal calcinosis; steatocystoma multiplex; and sarcoidosis (although uncommon for the site), given the history of pulmonary involvement. We considered a diagnosis of condyloma acuminatum, but the lesions were too shiny and smooth. On histology, condyloma acuminatum shows a hyperkeratotic and parakeratotic stratum corneum, an exophytic growth with marked acanthosis, and superficially located koilocytes. Morphologically, our patient's lesions resembled genital lichen planus. However, Wickham striae were absent, and our patient's lesions were asymptomatic while lesions of lichen planus usually are pruritic. Histologically, lichen planus is characterized by hyperkeratosis, hypergranulosis, sawtooth rete ridges, and lichenoid interface inflammation. Idiopathic scrotal calcinosis also could be included in the differential; however, the lesions would look whiter and firmer than those of our patient, and biopsy will clearly show calcium deposition. Steatocystoma multiplex is another condition that can affect the scrotum, along with the trunk, axillae, extremities, and neck. However, the lesions are expected to discharge oily material if squeezed and have a characteristic corrugated eosinophilic cuticle lining a cyst histologically.  

Although it is undetermined if the risk for systemic involvement increases in patients with cutaneous sarcoidosis, evaluation for probable systemic involvement is necessary.¹ Because cutaneous sarcoidosis generally can precede any systemic involvement, it would be reasonable to consider skin biopsies in patients who present with atypical wartlike lesions on the scrotum and penis to rule out sarcoidosis. 

The Diagnosis: Cutaneous Sarcoidosis  

Histologic examination of the shave biopsy showed focal parakeratosis, irregular epidermal hyperplasia, and multiple noncaseating naked granulomas with occasional multinucleated giant cells in the dermis (Figure, A). The granulomas were surrounded by mild lymphocytic infiltration with rare eosinophils (Figure, B). Periodic acid-Schiff and Fite stains were negative for organisms, and polariscopic examination was negative; these findings confirmed the diagnosis of cutaneous sarcoidosis. Topical or intralesional steroids were recommended, but our patient declined treatment given that the lesions were asymptomatic.  

Sarcoidosis is a multisystem granulomatous disease of unknown etiology that affects the skin in approximately 25% of patients.¹ Cutaneous lesions manifest in 2 forms: specific and nonspecific. Noncaseating granulomas are considered specific. Nonspecific lesions include erythema nodosum, calcinosis cutis, Sweet syndrome, and nail clubbing. The most common sites of specific sarcoidosis lesions include the face, lips, neck, upper trunk, and extremities. Few cases have reported cutaneous sarcoidosis involving the genitalia; most reports describe vulvar cutaneous sarcoidosis.^2-4 Although there have been reports of sarcoidosis involving the epididymis and testes, which presented as scrotal masses, cutaneous scrotal involvement with the skin as the primary site of involvement is rare.^5,6 McLaughlin et al⁵ reported an extensive, pruritic, and eczematous eruption of the scrotum with associated edema and tenderness. Wei et al⁶ reported cutaneous sarcoidosis in the form of multiple indurated papules involving the penis and scrotum, similar to our case.  

Comparing our patient to the case reported by Wei et al,⁶ both patients had Fitzpatrick skin type V or VI and systemic involvement including pulmonary disease. However, Wei et al⁶ did not clearly mention if the cutaneous manifestations preceded the diagnosis of systemic sarcoidosis or if they were present at the time of the diagnosis. Our patient developed cutaneous lesions 4 years after being diagnosed with systemic sarcoidosis from hilar lymphadenopathy. In addition to the scrotal lesions, he also had a lesion of lupus pernio presenting as a violaceous to brown plaque on the tip of the nose. Although both patients denied pruritus, the other patient's lesions were painful.⁶ Wei et al⁶ mentioned that treatment with topical, intralesional, and systemic steroids failed, and the patient's lesions continued to progress. Generally, topical and intralesional steroids are considered mainstay treatment of cutaneous sarcoidosis despite insufficient data to support their efficacy.⁷  

The differential diagnosis of papules on the scrotum can be broad. Our provisional diagnoses for this particular morphology of small, flesh-colored, shiny, polygonal, flat-topped papules included condyloma acuminatum; lichen planus; idiopathic scrotal calcinosis; steatocystoma multiplex; and sarcoidosis (although uncommon for the site), given the history of pulmonary involvement. We considered a diagnosis of condyloma acuminatum, but the lesions were too shiny and smooth. On histology, condyloma acuminatum shows a hyperkeratotic and parakeratotic stratum corneum, an exophytic growth with marked acanthosis, and superficially located koilocytes. Morphologically, our patient's lesions resembled genital lichen planus. However, Wickham striae were absent, and our patient's lesions were asymptomatic while lesions of lichen planus usually are pruritic. Histologically, lichen planus is characterized by hyperkeratosis, hypergranulosis, sawtooth rete ridges, and lichenoid interface inflammation. Idiopathic scrotal calcinosis also could be included in the differential; however, the lesions would look whiter and firmer than those of our patient, and biopsy will clearly show calcium deposition. Steatocystoma multiplex is another condition that can affect the scrotum, along with the trunk, axillae, extremities, and neck. However, the lesions are expected to discharge oily material if squeezed and have a characteristic corrugated eosinophilic cuticle lining a cyst histologically.  

Although it is undetermined if the risk for systemic involvement increases in patients with cutaneous sarcoidosis, evaluation for probable systemic involvement is necessary.¹ Because cutaneous sarcoidosis generally can precede any systemic involvement, it would be reasonable to consider skin biopsies in patients who present with atypical wartlike lesions on the scrotum and penis to rule out sarcoidosis. 

The Diagnosis: Cutaneous Sarcoidosis  

Histologic examination of the shave biopsy showed focal parakeratosis, irregular epidermal hyperplasia, and multiple noncaseating naked granulomas with occasional multinucleated giant cells in the dermis (Figure, A). The granulomas were surrounded by mild lymphocytic infiltration with rare eosinophils (Figure, B). Periodic acid-Schiff and Fite stains were negative for organisms, and polariscopic examination was negative; these findings confirmed the diagnosis of cutaneous sarcoidosis. Topical or intralesional steroids were recommended, but our patient declined treatment given that the lesions were asymptomatic.  

Sarcoidosis is a multisystem granulomatous disease of unknown etiology that affects the skin in approximately 25% of patients.¹ Cutaneous lesions manifest in 2 forms: specific and nonspecific. Noncaseating granulomas are considered specific. Nonspecific lesions include erythema nodosum, calcinosis cutis, Sweet syndrome, and nail clubbing. The most common sites of specific sarcoidosis lesions include the face, lips, neck, upper trunk, and extremities. Few cases have reported cutaneous sarcoidosis involving the genitalia; most reports describe vulvar cutaneous sarcoidosis.^2-4 Although there have been reports of sarcoidosis involving the epididymis and testes, which presented as scrotal masses, cutaneous scrotal involvement with the skin as the primary site of involvement is rare.^5,6 McLaughlin et al⁵ reported an extensive, pruritic, and eczematous eruption of the scrotum with associated edema and tenderness. Wei et al⁶ reported cutaneous sarcoidosis in the form of multiple indurated papules involving the penis and scrotum, similar to our case.  

Comparing our patient to the case reported by Wei et al,⁶ both patients had Fitzpatrick skin type V or VI and systemic involvement including pulmonary disease. However, Wei et al⁶ did not clearly mention if the cutaneous manifestations preceded the diagnosis of systemic sarcoidosis or if they were present at the time of the diagnosis. Our patient developed cutaneous lesions 4 years after being diagnosed with systemic sarcoidosis from hilar lymphadenopathy. In addition to the scrotal lesions, he also had a lesion of lupus pernio presenting as a violaceous to brown plaque on the tip of the nose. Although both patients denied pruritus, the other patient's lesions were painful.⁶ Wei et al⁶ mentioned that treatment with topical, intralesional, and systemic steroids failed, and the patient's lesions continued to progress. Generally, topical and intralesional steroids are considered mainstay treatment of cutaneous sarcoidosis despite insufficient data to support their efficacy.⁷  

The differential diagnosis of papules on the scrotum can be broad. Our provisional diagnoses for this particular morphology of small, flesh-colored, shiny, polygonal, flat-topped papules included condyloma acuminatum; lichen planus; idiopathic scrotal calcinosis; steatocystoma multiplex; and sarcoidosis (although uncommon for the site), given the history of pulmonary involvement. We considered a diagnosis of condyloma acuminatum, but the lesions were too shiny and smooth. On histology, condyloma acuminatum shows a hyperkeratotic and parakeratotic stratum corneum, an exophytic growth with marked acanthosis, and superficially located koilocytes. Morphologically, our patient's lesions resembled genital lichen planus. However, Wickham striae were absent, and our patient's lesions were asymptomatic while lesions of lichen planus usually are pruritic. Histologically, lichen planus is characterized by hyperkeratosis, hypergranulosis, sawtooth rete ridges, and lichenoid interface inflammation. Idiopathic scrotal calcinosis also could be included in the differential; however, the lesions would look whiter and firmer than those of our patient, and biopsy will clearly show calcium deposition. Steatocystoma multiplex is another condition that can affect the scrotum, along with the trunk, axillae, extremities, and neck. However, the lesions are expected to discharge oily material if squeezed and have a characteristic corrugated eosinophilic cuticle lining a cyst histologically.  

Although it is undetermined if the risk for systemic involvement increases in patients with cutaneous sarcoidosis, evaluation for probable systemic involvement is necessary.¹ Because cutaneous sarcoidosis generally can precede any systemic involvement, it would be reasonable to consider skin biopsies in patients who present with atypical wartlike lesions on the scrotum and penis to rule out sarcoidosis. 

The Diagnosis: Epithelioid Histiocytoma 

Epithelioid histiocytoma (EH), also known as epithelioid cell histiocytoma or epithelioid fibrous histiocytoma, is a rare benign fibrohistiocytic tumor first described in 1989.¹ Epithelioid histiocytoma commonly presents in middle-aged adults with a slight predilection for males.² The most frequently affected site is the lower extremity. The arms, trunk, head and neck, groin, and tongue also can be involved.^3,4 It usually presents as a solitary asymptomatic papule or nodule, though cases with multiple lesions have been reported.⁵ Anaplastic lymphoma kinase rearrangement and overexpression have been confirmed and suggest that EH is distinct from conventional cutaneous fibrous histiocytoma.⁵  

Histologically, EH appears as an exophytic, symmetric, and well-demarcated dermal nodule with a classic epidermal collarette. Prominent vascularity with perivascular accentuation of the epithelioid tumor cells is common. Older lesions may be hyalinized and sclerotic. Epithelioid cells commonly account for more than 50% of the tumor and are characterized by eosinophilic cytoplasm, vesicular nuclei, and small eosinophilic nucleoli. A small population of lymphocytes and mast cells are variably present (quiz image, bottom).^1-3,7 A predominantly spindle cell variant has been reported.⁸ Other histopathologic variants include granular cell,⁹ cellular,¹⁰ and EH with perineuriomalike growth.¹¹ Immunohistochemical staining shows anaplastic lymphoma kinase positivity in most cases, and more than half of cases stain positive for factor XIIIa and epithelial membrane antigen. Tumor cells consistently are negative for desmin and cytokeratins.^6,10,12 Excision is curative.⁸  

Polypoid Spitz nevus (PSN) is a benign nevus with a conspicuous polypoid or papillary exophytic architecture. The term was coined in 2000 by Fabrizi and Massi.¹³ Spitz nevus is a benign acquired melanocytic tumor that typically presents in children and adolescents and has a wide histologic spectrum.¹⁴ There is some debate on this entity, as some authors do not regard PSN as a distinct histologic variant; thus, it seems underreported in the literature.¹⁵ In a review of 349 cases of Spitz nevi, the authors found 7 cases of PSN.¹⁶ In another review of 74 cases of intradermal Spitz nevi, 14 cases of PSN were identified.¹⁴ This polypoid variant is easily mistaken for a polypoid melanoma because it can show cytologic atypia with large nuclei. Polypoid Spitz nevus usually lacks mitoses, notable pleomorphism, and sheetlike growth, unlike melanoma (Figure 1).^13,14  

Myopericytoma is an uncommon benign mesenchymal neoplasm that typically presents as a solitary, slowly enlarging and painless nodule with a predilection for the lower extremities, usually in adult males.^17-20 Histologically, it consists of a well-circumscribed nodule with numerous thin-walled vessels and a proliferation of ovoid to spindled myopericytes exhibiting a concentric perivascular growth pattern (Figure 2). Myopericytoma usually is positive for smooth muscle actin and h-caldesmon but is negative or only focally positive for desmin. The prognosis is good with rare recurrence, despite incomplete excision.^17,18 

Solitary reticulohistiocytoma is a rare benign form of non-Langerhans cell histiocytosis.^21,22 Unlike its multicentric counterpart, solitary reticulohistiocytoma rarely is associated with systemic disease. It presents as a small, dome-shaped, painless papule or nodule that can affect any part of the body.^22,23 Solitary reticulohistiocytoma characteristically demonstrates cells with a ground glass-like appearance and 2-toned cytoplasm. A mixed inflammatory infiltrate including neutrophils, eosinophils, and lymphocytes commonly is present (Figure 3). The epithelioid histiocytes are positive for vimentin and histiocytic markers including CD68 and CD163.²²  

Solitary fibrous tumor (SFT) is an uncommon mesenchymal fibroblastic neoplasm that can arise at almost any anatomic site.²⁴ Cutaneous SFTs are more common in women, most often involve the head, and appear to behave in an indolent manner.²⁵ Solitary fibrous tumors are translocation-associated neoplasms with a NAB2-STAT6 gene fusion.²⁶ The classic histology of SFT is a spindled fibroblastic proliferation arranged in a "patternless pattern" with interspersed stag horn-like, thin-walled blood vessels (Figure 4). Tumor cells usually are positive for CD34, CD99, and Bcl-2.²⁷ In addition, STAT6 immunoreactivity is useful in diagnosis of SFT.²⁵

The Diagnosis: Epithelioid Histiocytoma 

Epithelioid histiocytoma (EH), also known as epithelioid cell histiocytoma or epithelioid fibrous histiocytoma, is a rare benign fibrohistiocytic tumor first described in 1989.¹ Epithelioid histiocytoma commonly presents in middle-aged adults with a slight predilection for males.² The most frequently affected site is the lower extremity. The arms, trunk, head and neck, groin, and tongue also can be involved.^3,4 It usually presents as a solitary asymptomatic papule or nodule, though cases with multiple lesions have been reported.⁵ Anaplastic lymphoma kinase rearrangement and overexpression have been confirmed and suggest that EH is distinct from conventional cutaneous fibrous histiocytoma.⁵  

Histologically, EH appears as an exophytic, symmetric, and well-demarcated dermal nodule with a classic epidermal collarette. Prominent vascularity with perivascular accentuation of the epithelioid tumor cells is common. Older lesions may be hyalinized and sclerotic. Epithelioid cells commonly account for more than 50% of the tumor and are characterized by eosinophilic cytoplasm, vesicular nuclei, and small eosinophilic nucleoli. A small population of lymphocytes and mast cells are variably present (quiz image, bottom).^1-3,7 A predominantly spindle cell variant has been reported.⁸ Other histopathologic variants include granular cell,⁹ cellular,¹⁰ and EH with perineuriomalike growth.¹¹ Immunohistochemical staining shows anaplastic lymphoma kinase positivity in most cases, and more than half of cases stain positive for factor XIIIa and epithelial membrane antigen. Tumor cells consistently are negative for desmin and cytokeratins.^6,10,12 Excision is curative.⁸  

Polypoid Spitz nevus (PSN) is a benign nevus with a conspicuous polypoid or papillary exophytic architecture. The term was coined in 2000 by Fabrizi and Massi.¹³ Spitz nevus is a benign acquired melanocytic tumor that typically presents in children and adolescents and has a wide histologic spectrum.¹⁴ There is some debate on this entity, as some authors do not regard PSN as a distinct histologic variant; thus, it seems underreported in the literature.¹⁵ In a review of 349 cases of Spitz nevi, the authors found 7 cases of PSN.¹⁶ In another review of 74 cases of intradermal Spitz nevi, 14 cases of PSN were identified.¹⁴ This polypoid variant is easily mistaken for a polypoid melanoma because it can show cytologic atypia with large nuclei. Polypoid Spitz nevus usually lacks mitoses, notable pleomorphism, and sheetlike growth, unlike melanoma (Figure 1).^13,14  

Myopericytoma is an uncommon benign mesenchymal neoplasm that typically presents as a solitary, slowly enlarging and painless nodule with a predilection for the lower extremities, usually in adult males.^17-20 Histologically, it consists of a well-circumscribed nodule with numerous thin-walled vessels and a proliferation of ovoid to spindled myopericytes exhibiting a concentric perivascular growth pattern (Figure 2). Myopericytoma usually is positive for smooth muscle actin and h-caldesmon but is negative or only focally positive for desmin. The prognosis is good with rare recurrence, despite incomplete excision.^17,18 

Solitary reticulohistiocytoma is a rare benign form of non-Langerhans cell histiocytosis.^21,22 Unlike its multicentric counterpart, solitary reticulohistiocytoma rarely is associated with systemic disease. It presents as a small, dome-shaped, painless papule or nodule that can affect any part of the body.^22,23 Solitary reticulohistiocytoma characteristically demonstrates cells with a ground glass-like appearance and 2-toned cytoplasm. A mixed inflammatory infiltrate including neutrophils, eosinophils, and lymphocytes commonly is present (Figure 3). The epithelioid histiocytes are positive for vimentin and histiocytic markers including CD68 and CD163.²²  

Solitary fibrous tumor (SFT) is an uncommon mesenchymal fibroblastic neoplasm that can arise at almost any anatomic site.²⁴ Cutaneous SFTs are more common in women, most often involve the head, and appear to behave in an indolent manner.²⁵ Solitary fibrous tumors are translocation-associated neoplasms with a NAB2-STAT6 gene fusion.²⁶ The classic histology of SFT is a spindled fibroblastic proliferation arranged in a "patternless pattern" with interspersed stag horn-like, thin-walled blood vessels (Figure 4). Tumor cells usually are positive for CD34, CD99, and Bcl-2.²⁷ In addition, STAT6 immunoreactivity is useful in diagnosis of SFT.²⁵

The Diagnosis: Epithelioid Histiocytoma 

Epithelioid histiocytoma (EH), also known as epithelioid cell histiocytoma or epithelioid fibrous histiocytoma, is a rare benign fibrohistiocytic tumor first described in 1989.¹ Epithelioid histiocytoma commonly presents in middle-aged adults with a slight predilection for males.² The most frequently affected site is the lower extremity. The arms, trunk, head and neck, groin, and tongue also can be involved.^3,4 It usually presents as a solitary asymptomatic papule or nodule, though cases with multiple lesions have been reported.⁵ Anaplastic lymphoma kinase rearrangement and overexpression have been confirmed and suggest that EH is distinct from conventional cutaneous fibrous histiocytoma.⁵  

Histologically, EH appears as an exophytic, symmetric, and well-demarcated dermal nodule with a classic epidermal collarette. Prominent vascularity with perivascular accentuation of the epithelioid tumor cells is common. Older lesions may be hyalinized and sclerotic. Epithelioid cells commonly account for more than 50% of the tumor and are characterized by eosinophilic cytoplasm, vesicular nuclei, and small eosinophilic nucleoli. A small population of lymphocytes and mast cells are variably present (quiz image, bottom).^1-3,7 A predominantly spindle cell variant has been reported.⁸ Other histopathologic variants include granular cell,⁹ cellular,¹⁰ and EH with perineuriomalike growth.¹¹ Immunohistochemical staining shows anaplastic lymphoma kinase positivity in most cases, and more than half of cases stain positive for factor XIIIa and epithelial membrane antigen. Tumor cells consistently are negative for desmin and cytokeratins.^6,10,12 Excision is curative.⁸  

Polypoid Spitz nevus (PSN) is a benign nevus with a conspicuous polypoid or papillary exophytic architecture. The term was coined in 2000 by Fabrizi and Massi.¹³ Spitz nevus is a benign acquired melanocytic tumor that typically presents in children and adolescents and has a wide histologic spectrum.¹⁴ There is some debate on this entity, as some authors do not regard PSN as a distinct histologic variant; thus, it seems underreported in the literature.¹⁵ In a review of 349 cases of Spitz nevi, the authors found 7 cases of PSN.¹⁶ In another review of 74 cases of intradermal Spitz nevi, 14 cases of PSN were identified.¹⁴ This polypoid variant is easily mistaken for a polypoid melanoma because it can show cytologic atypia with large nuclei. Polypoid Spitz nevus usually lacks mitoses, notable pleomorphism, and sheetlike growth, unlike melanoma (Figure 1).^13,14  

Myopericytoma is an uncommon benign mesenchymal neoplasm that typically presents as a solitary, slowly enlarging and painless nodule with a predilection for the lower extremities, usually in adult males.^17-20 Histologically, it consists of a well-circumscribed nodule with numerous thin-walled vessels and a proliferation of ovoid to spindled myopericytes exhibiting a concentric perivascular growth pattern (Figure 2). Myopericytoma usually is positive for smooth muscle actin and h-caldesmon but is negative or only focally positive for desmin. The prognosis is good with rare recurrence, despite incomplete excision.^17,18 

Solitary reticulohistiocytoma is a rare benign form of non-Langerhans cell histiocytosis.^21,22 Unlike its multicentric counterpart, solitary reticulohistiocytoma rarely is associated with systemic disease. It presents as a small, dome-shaped, painless papule or nodule that can affect any part of the body.^22,23 Solitary reticulohistiocytoma characteristically demonstrates cells with a ground glass-like appearance and 2-toned cytoplasm. A mixed inflammatory infiltrate including neutrophils, eosinophils, and lymphocytes commonly is present (Figure 3). The epithelioid histiocytes are positive for vimentin and histiocytic markers including CD68 and CD163.²²  

Solitary fibrous tumor (SFT) is an uncommon mesenchymal fibroblastic neoplasm that can arise at almost any anatomic site.²⁴ Cutaneous SFTs are more common in women, most often involve the head, and appear to behave in an indolent manner.²⁵ Solitary fibrous tumors are translocation-associated neoplasms with a NAB2-STAT6 gene fusion.²⁶ The classic histology of SFT is a spindled fibroblastic proliferation arranged in a "patternless pattern" with interspersed stag horn-like, thin-walled blood vessels (Figure 4). Tumor cells usually are positive for CD34, CD99, and Bcl-2.²⁷ In addition, STAT6 immunoreactivity is useful in diagnosis of SFT.²⁵