Extramedullary plasmacytomas are rare malignant neoplasms that can arise in various organs; however, lymph node involvement is uncommon. The cervical lymph nodes are most frequently affected. We present the case of a 68-year-old female diagnosed with a primary extramedullary plasmacytoma involving multiple lymph nodes, primarily in the cervical region.

A 68-year-old female patient presented with a one-month history of progressive enlargement and painful swelling of the right subclavicular and cervical areas. Imaging revealed pathological lymphadenopathy, and excisional biopsy was performed from the right cervical level 5 lymph node. Histopathological analysis confirmed the diagnosis of a plasmacytoma. A subsequent bone marrow biopsy revealed normocellular marrow without any evidence of infiltration. Positron emission tomography-CT staging demonstrated further lymph node involvement in the right cervical, subclavicular, supraclavicular, axillary, and mediastinal regions.

This case was classified as a primary extramedullary plasmacytoma of the lymph nodes, given the absence of multiple myeloma markers in the bone marrow and immunoelectrophoretic studies. Lymph node plasmacytomas are exceedingly rare, comprising approximately 2% of all extramedullary plasmacytomas. Clinically, these patients often present with localized masses and minimal systemic symptoms. While recurrence is possible, primary lymph node plasmacytomas rarely progress to multiple myeloma and are associated with a more favorable prognosis than other solitary extramedullary plasmacytomas. The distinct clinical behavior of these lesions suggests that they may represent a unique subset of plasmacytomas with a lower risk of transformation into multiple myeloma. Most patients respond well to surgical excision, with minimal risk of recurrence or progression, even in the absence of adjuvant therapy. Although some patients develop osseous plasmacytomas, none have progressed to multiple myeloma in reported series.