MUM-1 and bcl-2 Positive Primary Diffuse Large B Cell Non-Hodgkin's Lymphoma of the Colon.

Primary diffuse large B cell lymphoma (DLBCL) presents as a nodal and extranodal disease. The most common extranodal site is the gastrointestinal tract (GI), with the stomach most frequently involved, followed by the small bowel. Primary DLBCL of the large bowel accounts for 0.2%-1.2% of all colonic tumors. We present two patients who underwent radical resections of right colonic tumors. They were diagnosed with primary colonic DLBCL following histological and immunohistochemical testing of the excised tissues, and were determined as being in stage IIE of the disease. The tumors expressed CD20 markers. Both received multi-agent chemotherapy with combined immunotherapy and remain in complete remission at 4 and 5 years.