Case report: gastric plasmacytoma resistant to radiation therapy

Plasma cell neoplasms are a group of diseases involving the malignant proliferation of plasma cells. One common type of plasma cell neoplasm is multiple myeloma, which typically occurs diffusely in the bone marrow. It can manifest with a variety of presentations, including bone pain, fractures, anemia, infection, hypercalcemia, and renal failure. A less common type of plasma cell neoplasm is the solitary plasmacytoma, which is a local proliferation of plasma cells in the bone or extramedullary tissues. They rarely recur after local radiation therapy.An 83-year-old woman was noted on routine labwork to have elevated total serum protein, and serum immunofixation confirmed IgG/Kappa paraprotein. There was no evidence of end-organ damage characteristic of myeloma: hypercalcemia, renal dysfunction, anemia, or bone lesions. She was diagnosed with monoclonal gammopathy of undetermined significance and placed on observation. Seven years later, she developed mild anemia and an increasing M spike. No abnormalities were found on bone marrow biopsy apart from mildly increased plasma cell proliferation (7-10% of total cells). A PET scan showed increased gastric uptake, concerning for possible gastric malignancy. Upper gastrointestinal endoscopic ultrasound revealed extrinsic compression of the stomach fundus and body due to a 40 mm mass and associated adenopathy. Pathology revealed a kappa-restricted plasma cell neoplasm positive for CD138.The patient underwent radiation therapy localized to the gastric area. Subsequent evaluation revealed a persistent gastric mass. Attempted biopsy resulted in a gastrointestinal bleed, rendering her unable to undergo treatment with lenalidomide and aspirin. She is currently undergoing chemotherapy with bortezomib, cyclophosphamide, and dexamethasone. The case illustrates the potential diversity of plasma cell dyscrasia clinical manifestations. Gastric plasmacytomas are an uncommon type of extramedullary plasmacytoma, particularly rare when resistant to radiation therapy.