Lymphomas of mucosa-associated lymphoid tissue (MALT) comprise 7% of all newly diagnosed non-Hodgkin's lymphomas. Helicobacter pylori (H. pylori) negative gastric MALT lymphomas account for 28 to 45% of gastric MALT lymphomas. H. pylori infection has a close relationship with most gastric low-grade B cell lymphomas of the MALT type. Monoclonal gammopathy can be seen in 36% of the patients and negatively associated with responses to eradication of H. pylori in gastric MALT lymphoma. Here, we describe a case of H. pylori negative MALT lymphoma that arose from the stomach with massive plasmacytic differentiation mimicking an extramedullary plasmacytoma with monoclonal gammopathy, and that was cured by total gastrectomy, chemotherapy and radiotherapy. (Korean J Hematol 2009;44:261-267.)

Keywords: Helicobacter pylori negative, Gastric B cell lymphoma of mucosa-associated lymphoid tissue type, Monoclonal gammopathy