Gastric MALT lymphoma presenting as Waldenström's macroglobulinemia without bone marrow involvement

We report a case of gastric mucosa-associated lymphoid tissue (MALT) lymphoma with macroglobulinemia in a 59-year-old man who presented with melena. A computed tomography scan of the abdomen showed irregular thickening of the wall of the stomach, and endoscopic examination disclosed enlarged and inflammatory folds of the fundus. Histopathologic examination of gastric samples showed mucosal infiltration by small lymphocytes, which were positive for CD20 and negative for CD10 and CD23, confirming the diagnosis of gastric MALT lymphoma. Serum electrophoresis detected a monoclonal peak and immunoelectrophoresis revealed an immunoglobulin M kappa component. Bone marrow aspirate and biopsy results were normal. The patient received chemotherapy. After treatment, he was in complete remission, and the serum monoclonal component had disappeared. Our observation is uncommon because of important macroglobulinemia occurring in gastric MALT lymphoma without bone marrow involvement.