Mucosa-Associated Lymphoid Tissue (MALT) Lymphoma of the Colon: A Case Report and a Literature Review.

BACKGROUND Non-Hodgkin lymphoma (NHL) is a well-known hematologic malignancy. The gastrointestinal (GI) tract is the most commonly involved extra nodal site. MALT lymphomas are uncommon, accounting for 5% of all NHL. Gastric mucosa-associated lymphoid tissue (MALT) lymphoma is the prototype seen in association with Helicobacter pylori. Colonic MALT lymphoma is rare and comprises only 2.5% of the MALT lymphomas. Its etiology and treatment is not well established.  CASE REPORT A 56-year-old Hispanic woman presented to the clinic with symptoms of chronic epigastric pain for the past three years and a 13-pound weight loss over the past two months. The patient did not have any prior medical conditions. Her systemic examination was unremarkable, while her routine labs revealed mild anemia. An upper endoscopy and colonoscopy for colorectal cancer screening were performed revealing erosive gastropathy with duodenal ulcers and a 5 cm broad based polypoid mass in the hepatic flexure respectively. Computed tomography (CT) of the abdomen revealed a round, well demarcated mass at the hepatic flexure of the colon. The histopathology and immunophenotyping were consistent with extra nodal marginal zone of MALT lymphoma. Stool testing for H. pylori was positive. The patient received two weeks of H. pylori eradication therapy and four cycles of rituximab. Repeat colonoscopy after completion of chemotherapy showed complete resolution of the MALT lymphoma.   CONCLUSIONS Unlike gastric MALT lymphoma, treatment of colonic MALT lymphoma is not standardized. Chemotherapy and surgical resection have been utilized to successfully treat it. Only a handful of cases have reported successful treatment of colonic MALT lymphoma with rituximab monotherapy.