A Case of Primary Gastric Extramedullary Plasmacytoma with Skin Invasion Occurring 6 Years after Surgery

Abstract

Primary gastric extramedullary plasmacytoma is a rare neoplasm. We herein report a case of primary gastric extramedullary plasmacytoma with skin invasion occurring 6 years after surgery. A 65‑year‑old male presented with tarry stool. Endoscopy showed a nodular mass in the stomach. 18F‑fluorodeoxyglucose positron emission tomography（FDG‑PET）revealed abnormal accumulation corresponding to the lesion, suggesting malignancy. Due to progressive anemia caused by bleeding from the tumor, emergency surgery was performed. Suspecting infiltration into the body and tail of the pancreas, we conducted a total gastrectomy with regional lymph node dissection, along with resection of the body and tail of the pancreas and spleen. Pathological examination revealed proliferation of tumor cells resembling plasma cells, and immunohistochemical staining demonstrated monoclonal production of IgG and λ chains, leading to the diagnosis of primary gastric extramedullary plasmacytoma. No adjuvant therapy was administered, and skin invasion occurred in the sixth year after surgery. Primary gastric extramedullary plasmacytoma is infrequently reported, and its pathophysiology is not yet fully understood. Prolonged and vigilant postoperative observation is essential due to the limited knowledge about the condition.