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Background
Marginal zone lymphoma (MZL) is an indolent B-cell non-Hodgkin lymphoma most commonly arising in mucosal, nodal, or splenic tissues. While extranodal presentations are recognized, involvement of the sciatic foramen is exceedingly rare. We present a unique case of stage IV MZL with primary involvement of the left sciatic foramen, identified incidentally during urologic evaluation.
Case Presentation
A 74-year-old male patient was referred for hematologic evaluation after imaging revealed a left sciatic foraminal mass during work-up for elevated PSA. CT abdomen/pelvis revealed a 4.7 cm mass in the left sciatic foramen. Follow-up PET-CT confirmed hypermetabolic activity in the mass, with additional areas of uptake in the right ilium and pleural- pericardial regions. The patient was asymptomatic and denied B-symptoms. CT-guided biopsy of the sciatic mass revealed low-grade B-cell lymphoma. Flow cytometry showed a CD20-positive, CD5-negative, CD10-negative, lambda light chain–restricted population consistent with marginal zone lymphoma. Laboratory studies demonstrated iron deficiency anemia, with otherwise unremarkable counts and chemistries. He was started on monotherapy with rituximab for four cycles. He tolerated treatment well. Interval PET imaging in April 2025 showed stable disease in the sciatic foramen and mild improvement in pleural- pericardial uptake. He is planned to start obinutuzumab in the upcoming month.
Discussion
This case illustrates a rare anatomic presentation of MZL, likely representing primary sciatic foramen involvement. The presence of additional PETavid lesions complicates staging, raising consideration of stage I vs. III/IV disease. Biopsy was limited to the sciatic lesion, and no bone marrow sampling was performed. Given the patient’s excellent performance status, absence of symptoms, and low tumor burden, single-agent rituximab was chosen initially in accordance with NCCN guidelines.
Conclusions
Sciatic foramen involvement by MZL is an extremely rare occurrence and may mimic more common soft tissue or neurogenic tumors radiographically. This case underscores the importance of biopsy for diagnosis and the value of multidisciplinary care. In the veteran population, such incidental findings on imaging warrant comprehensive evaluation, particularly in atypical anatomical sites.
Background
Marginal zone lymphoma (MZL) is an indolent B-cell non-Hodgkin lymphoma most commonly arising in mucosal, nodal, or splenic tissues. While extranodal presentations are recognized, involvement of the sciatic foramen is exceedingly rare. We present a unique case of stage IV MZL with primary involvement of the left sciatic foramen, identified incidentally during urologic evaluation.
Case Presentation
A 74-year-old male patient was referred for hematologic evaluation after imaging revealed a left sciatic foraminal mass during work-up for elevated PSA. CT abdomen/pelvis revealed a 4.7 cm mass in the left sciatic foramen. Follow-up PET-CT confirmed hypermetabolic activity in the mass, with additional areas of uptake in the right ilium and pleural- pericardial regions. The patient was asymptomatic and denied B-symptoms. CT-guided biopsy of the sciatic mass revealed low-grade B-cell lymphoma. Flow cytometry showed a CD20-positive, CD5-negative, CD10-negative, lambda light chain–restricted population consistent with marginal zone lymphoma. Laboratory studies demonstrated iron deficiency anemia, with otherwise unremarkable counts and chemistries. He was started on monotherapy with rituximab for four cycles. He tolerated treatment well. Interval PET imaging in April 2025 showed stable disease in the sciatic foramen and mild improvement in pleural- pericardial uptake. He is planned to start obinutuzumab in the upcoming month.
Discussion
This case illustrates a rare anatomic presentation of MZL, likely representing primary sciatic foramen involvement. The presence of additional PETavid lesions complicates staging, raising consideration of stage I vs. III/IV disease. Biopsy was limited to the sciatic lesion, and no bone marrow sampling was performed. Given the patient’s excellent performance status, absence of symptoms, and low tumor burden, single-agent rituximab was chosen initially in accordance with NCCN guidelines.
Conclusions
Sciatic foramen involvement by MZL is an extremely rare occurrence and may mimic more common soft tissue or neurogenic tumors radiographically. This case underscores the importance of biopsy for diagnosis and the value of multidisciplinary care. In the veteran population, such incidental findings on imaging warrant comprehensive evaluation, particularly in atypical anatomical sites.
Background
Marginal zone lymphoma (MZL) is an indolent B-cell non-Hodgkin lymphoma most commonly arising in mucosal, nodal, or splenic tissues. While extranodal presentations are recognized, involvement of the sciatic foramen is exceedingly rare. We present a unique case of stage IV MZL with primary involvement of the left sciatic foramen, identified incidentally during urologic evaluation.
Case Presentation
A 74-year-old male patient was referred for hematologic evaluation after imaging revealed a left sciatic foraminal mass during work-up for elevated PSA. CT abdomen/pelvis revealed a 4.7 cm mass in the left sciatic foramen. Follow-up PET-CT confirmed hypermetabolic activity in the mass, with additional areas of uptake in the right ilium and pleural- pericardial regions. The patient was asymptomatic and denied B-symptoms. CT-guided biopsy of the sciatic mass revealed low-grade B-cell lymphoma. Flow cytometry showed a CD20-positive, CD5-negative, CD10-negative, lambda light chain–restricted population consistent with marginal zone lymphoma. Laboratory studies demonstrated iron deficiency anemia, with otherwise unremarkable counts and chemistries. He was started on monotherapy with rituximab for four cycles. He tolerated treatment well. Interval PET imaging in April 2025 showed stable disease in the sciatic foramen and mild improvement in pleural- pericardial uptake. He is planned to start obinutuzumab in the upcoming month.
Discussion
This case illustrates a rare anatomic presentation of MZL, likely representing primary sciatic foramen involvement. The presence of additional PETavid lesions complicates staging, raising consideration of stage I vs. III/IV disease. Biopsy was limited to the sciatic lesion, and no bone marrow sampling was performed. Given the patient’s excellent performance status, absence of symptoms, and low tumor burden, single-agent rituximab was chosen initially in accordance with NCCN guidelines.
Conclusions
Sciatic foramen involvement by MZL is an extremely rare occurrence and may mimic more common soft tissue or neurogenic tumors radiographically. This case underscores the importance of biopsy for diagnosis and the value of multidisciplinary care. In the veteran population, such incidental findings on imaging warrant comprehensive evaluation, particularly in atypical anatomical sites.