S3779 The Unexpected: A Rare Case of Colonic MALT Lymphoma

Introduction: Extranodal marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT) is 1 of the most common histologic subtypes of primary gastric lymphomas. MALT lymphomas are rare and account for only 5% of all non-Hodgkin’s lymphomas and are considered low-grade, with their occurrence strongly correlated with presence of H. pylori infection. These lymphomas occur in the stomach in 60-75% of the cases with only 2.5% of cases developing in the colon. When the colon is involved, patients present with gastrointestinal bleeding, changes to bowel habits, and abdominal pain while few remain asymptomatic. We present a case of a 71-year-old man with alternating bowel habits, found to have colonic MALT lymphoma, without history of H. pylori. Case Description/Methods: A 71-year-old man with history of diabetes presented for routine cancer screening and reported alternating bowel habits without overt bleeding or constitutional symptoms. He also reported excessive belching and bloating lasting 1 month. Labs demonstrated iron deficiency anemia. He subsequently underwent both EGD, which demonstrated a nonobstructive Schatzki’s ring, hiatal hernia, mild gastritis, and negative for H. pylori and a colonoscopy which revealed a total of 18 inflammatory appearing polyps. All of them were removed and were positive for low grade MALT lymphoma in the cecum, ascending, transverse and descending colon. The rectal polyps were benign and CMV stains were positive. A computed tomography chest, abdomen and pelvis demonstrated a 7 mm omental lymph node and 8 mm mesenteric lymph node. He was referred to heme/onc and pending treatment initiation. Discussion: While MALT lymphomas rarely occur, the most common site is the stomach with an incidence of 60-75% and typically involve a history of chronic H. pylori, in 90% of cases. This case is unique since the patient was negative for H. pylori and had no known history. Also, while there is no proven cause and effect between CMV and MALT lymphomas, it can be suspected that the underlying inflammatory environment and immunosuppression created by CMV in an individual who is already immunocompromised could possibly be associated with development of MALT lymphoma in colon. These lymphomas are also not well defined endoscopically, but usually appear as a singular polypoid lesion. Our patient was found to have multiple inflammatory appearing polyps, which also differs from current literature.