Secondary mucosa-associated lymphoid tissue (MALT) lymphoma of the colon.

Mucosa-associated lymphoid tissue (MALT)-type lymphomas most commonly occur in the stomach and have been associated with Helicobacter pylori infection. However, MALT-type lymphoma of the colon is a rare entity. It commonly manifests with symptoms of weight loss, low-grade fever, constipation, melena, and hematochezia. Unlike gastric lymphoma, it is difficult to detect MALT-type lymphoma of the colon by imaging. Colonoscopy may reveal lesions whose biopsy most commonly shows abundant B lymphocytes. There is no universal immunohistochemistry profile for MALT-type lymphoma but CD 20 staining is commonly seen. Trisomies and translocations have been described and their presence has been correlated with treatment response. Due to the rarity of colonic MALT-type lymphoma, no standard guidelines are available for its management. It often occurs individually and rarely occurs simultaneously with concurrent colon adenocarcinoma. This case report describes the presentation and clinical course of a secondary MALT-type lymphoma in a patient who underwent colectomy for a prior colon adenocarcinoma.