A rare presentation of biclonal gammopathy in primary mediastinal lymph node plasmacytoma: A case report

Primary plasmacytomas are localized proliferations of clonal plasma cells occurring in the absence of a systemic plasma cell dyscrasia, such as multiple myeloma. They most commonly manifest as solitary lesions in the bone or in the upper aerodigestive tract. Presentation in a lymph node is quite rare, especially when it involves the mediastinum. We report the case of a 32-year-old woman presenting with worsening dyspnea, cough, and chest discomfort, with radiologic evidence of mediastinal enlargement. An excisional biopsy of a large mediastinal mass revealed a plasma cell infiltrate, while protein electrophoresis analysis showed a biclonal gammopathy of the IgG kappa and IgA lambda type. She was treated with a myeloma-like regimen consisting of four cycles of bortezomib/dexamethasone followed by two cycles of thalidomide/prednisone, resulting in improvement of symptoms and complete resolution of lymphadenopathy. She remained in remission over 18 months following completion of therapy. This case report illustrates an unusual instance of biclonal gammopathy in primary mediastinal lymph node plasmacytoma, emphasizing its unique presentation and successful treatment through systemic therapy.