S1795 Incidental Finding of a MALT Lymphoma of the Rectum

Abstract

INTRODUCTION: Extranodal marginal zone lymphomas of the mucosa-associated lymphoid tissue (MALT) are a subtype of Non-Hodgkin lymphoma (NHL), accounting for only 5% of all NHL. MALT lymphomas can be found in different tissues of the body, the stomach being the most commonly affected gastrointestinal site. Primary colorectal MALT lymphoma is a rare entity and few cases have been reported in the literature; its presentation is often indistinguishable from that of other colonic malignancies, or it can be found incidentally during screening colonoscopies. CASE DESCRIPTION/METHODS: We report the case of an asymptomatic 51-year-old female with a family history of colorectal cancer who underwent routine screening colonoscopy. Prior colonoscopies performed since age 40 were unremarkable. Colonoscopy revealed a subepithelial nodule in the recto-sigmoid colon (Figure 1). Subsequently, a lower endoscopic ultrasound (EUS) was performed and revealed a 15 mm polypoid multi-lobulated lesion with central umbilication in the recto-sigmoid colon. Endosonographically, the lesion was hypoechoic, and it appeared to be confined to both the luminal interface/superficial mucosa and deep mucosa without evidence of extension into the submucosa or muscularis propria. The lesion was successfully removed in its entirety by endoscopic mucosal resection (EMR). The procedure was uneventful, and the patient was discharged home the same day. Pathology revealed large intestinal mucosa of the rectum with extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (Figure 2). Immunohistochemistry demonstrated lymphoid cells that were positive for CD20 (Figure 3), CD23, and BCL2 but negative for CD3, CD5, CD43, CD10, and BCL6; confirming the above diagnosis. Whole-body positron emission tomography did not reveal systemic extension. Repeat colonoscopy 3 months later revealed visually prominent infiltration at post-mucosectomy scar negative for residual lymphoma on biopsy. However, due to a strong concern for submucosal spread on site, a decision was made to start radiation therapy. DISCUSSION: The treatment for patients with MALT lymphoma includes surgical resection, chemotherapy, and radiation among others. However, due to the rarity of colonic MALT lymphomas, the optimal treatment modality for them is not well defined and though its prognosis tends to be excellent, periodic surveillance colonoscopies are needed due to increased risk for other primaries and localized recurrence or transformation into higher-grade disease in some instances.Figure 1.: A subepithelial nodule is seen in recto-sigmoid colon during endoscopy.Figure 2.: Rectal mucosa with dense infiltration of lymphoid cells (H&E, 50x).Figure 3.: Diffuse expression of CD20 on immunohistochemical staining suggests lymphoid infiltrate to be composed mostly of B-cells (50x).