Mucosa-Associated Lymphoid Tissue Lymphoma of the Rectum Incidentally Found in a Patient with Ulcerative Colitis

ABSTRACT

Introduction: Mucosa-associated lymphoid tissue (MALT) lymphomas are extra-nodal marginal zone B-cell lymphomas, most commonly found in the stomach, associated with Helicobacter pylori infections, and generally not linked with inflammatory bowel disease. Rectal MALT lymphoma is very uncommon and often associated with painful defecation, change in bowel habits, or rectal pressure/prolapse. Here, we present a rare case of an asymptomatic female with ulcerative colitis (UC) found to have benign-appearing rectal polyps during a routine screening colonoscopy. Case Description/Methods: The patient is a 56-year-old female with a history of left-sided UC, diagnosed in 1993, with one flare after receiving the 2nd dose of the Moderna COVID-19 vaccine, taking oral Olsalazine 500 mg twice daily, low-dose Prednisone, and mesalamine suppositories as needed presenting for screening colonoscopy. The patient was asymptomatic, citing regular non-bloody bowel movements and normal stool consistency. Colonoscopy revealed two 7 mm sessile, non-bleeding rectal polyps, surrounded by congested, erythematous, friable, and ulcerated mucosa in the rectosigmoid colon. Cold forceps biopsies were taken. Hematopathology evaluation of the routine colon biopsy samples revealed chronic nonspecific colitis while pathology of the rectal polyps showed marked lymphoplasmacytic infiltrate and extra-nodal marginal zone lymphoma of MALT. Ancillary studies, immunohistochemistry, and molecular studies for B-cell gene rearrangement confirmed extra-nodal marginal zone lymphoma of MALT with prominent plasmacytic differentiation. The patient was informed and close follow-up in Gastroenterology clinic was arranged. (Figure) Discussion: Rectal MALT lymphoma is rare with unclear management options. Treatments of UC include watchful waiting, surgical resection, endoscopic mucosal resection, radiation, and/or chemotherapy. Helicobacter pylori infections, though strongly linked with gastric MALT lymphoma, have not been shown to be strongly correlated with rectal MALT lymphoma. Given that patients with UC have chronic UCassociated colonic inflammation, lymphoma is often difficult to distinguish visually during colonoscopy, frequently masked by ulcerations and pseudo-polyps. In cases like these, more definitive treatments such as surgical resection could therefore be warranted. Long-term follow-up data is sparse and definitive management remains a clinical conundrum, thus these patients require reliable long-term multidisciplinary close follow-up. (Figure Presented).