Medical Student Weill Cornell Medical College New York, NY, US
Introduction: Plasmacytoma is a rare plasma cell tumor often seen as a complication of multiple myeloma (MM). While paraskeletal plasmacytomas (PPs) form in bones, extramedullary plasmacytomas (EMPs) form by hematogenous spread to soft tissues. Primary EMPs arise in the absence of systemic disease, whereas secondary EMPs are soft tissue metastases of MM. Peripheral nerve EMPs are difficult to distinguish from other peripheral nerve sheath tumors with imaging alone. To our knowledge, only one case of a primary peripheral nerve EMP has been reported in the English literature. Here, we discuss the first reported case of a secondary peripheral nerve EMP in the tibial nerve.
Methods: This case report was prepared following CARE guidelines. A literature review was conducted, which found no previously published cases with similar findings.
Results:
Case Presentation: A 70-year-old female with a history of relapsed/refractory MM presented with 19 months of worsening neuropathic right leg pain. MRI revealed a lesion in the right popliteal fossa that was consistent with a tibial nerve sheath tumor. The patient elected to proceed with surgical resection. Surgical resection was attempted, but frozen pathology revealed a plasma cell neoplasm with a high Ki67 proliferation rate, indicative of an EMP. Given the significant hemorrhagic, infiltrative, and proliferative nature of the tumor, resection was halted. Postoperatively, the patient experienced increased leg pain and received three courses of Teclistamab along with five fractions of radiation therapy (RT). Postoperative complications included a deep vein thrombosis (DVT) and two episodes of Grade I cytokine release syndrome (CRS). The patient continued treatment with Teclistamab and intravenous immunoglobulin (IVIG) as an outpatient.
Conclusion : This case underscores the importance of considering extramedullary plasmacytomas in the differential diagnosis of peripheral nerve sheath tumors, particularly in patients with MM. Further research is needed to establish a standard of care for EMPs in such uncommon locations.
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