Mucosa-associated lymphoid tissue lymphoma of the appendix vermiformis.

A 60-year-old woman with right lower abdominal pain was admitted to our hospital. Computed tomography demonstrated right hydronephrosis and an irregular mass of 4 x 3 cm adjacent to the ileocecal region and iliopsoas muscle. Preoperative serum soluble anti-interleukin-2 receptor antibody was elevated (689 U/ml). Laparotomy showed an appendiceal tumor invading the cecum, mesocolon, right ureter, and duodenum. Right hemicolectomy with partial resection of the right ureter was performed. Histologic examination revealed diffuse infiltration of centrocyte-like cells, scattered plasma cells, and immunoblasts. The centrocyte-like cells were immunohistochemically positive for CD20 and CD79a, and were negative for BCL2, CD3, CD5, and CD10; this was compatible with primary mucosa-associated lymphoid tissue (MALT) lymphoma. The patient has shown a favorable course without recurrence for 2 years postoperatively. This is the sixth documented case of primary MALT lymphoma of the appendix. The spectrum of sites in which gastrointestinal MALT lymphomas occur should be expanded to include the appendix.