Mimicking Lymphoma: A Rare Case of Extramedullary Plasmacytoma in Lymph Nodes on 18F-FDG PET/CT

Extramedullary plasmacytoma involving multiple lymph nodes is extremely rare. We report FDG PET/CT findings of multiple extramedullary plasmacytomas involving lymph nodes in a 71-year-old man. A chest CT scan revealed multiple enlarged lymph nodes in the right supraclavicular region, hilum, and mediastinum, merging into several soft tissue masses suggestive of lymphoma. On FDG PET/CT, these masses demonstrated intense 18 F-FDG uptake, mimicking aggressive lymphoma. No other abnormal tracer uptake was identified. Biopsy of the right supraclavicular lymph node confirmed the diagnosis of plasmacytoma.