A147 PRIMARY COLONIC MANTLE CELL LYMPHOMA: A RARE ENTITY

Abstract Background Mantle cell lymphoma (MCL) is an aggressive subtype of B-cell non-Hodgkin lymphoma (NHL), often diagnosed at later stages with secondary gastrointestinal (GI) involvement. Primary GI MCL is rare and is not often discussed in the literature. Aims To increase awareness of a rare condition that is likely to be encountered but can be challenging to diagnose. Methods Case report and review of the literature. Results Case Report A 78-year-old man with multiple untreated vascular risk factors including atrial fibrillation and type 2 diabetes presented with acute onset left hemiplegia, dysarthria, and imaging consistent with a left pontine stroke. As part of his workup he underwent a CT abdomen/pelvis identifying an 11 x 5 cm intraluminal mass in the transverse colon. Previous screening colonoscopies, for family history of colon cancer, were notable for tubular adenomas without high-grade dysplasia at 13, 12, 10, 7, and 2 years prior to admission. The patient had 16 pounds of weight loss without other constitutional symptoms, change in bowel habits or evidence of GI bleeding. Bloodwork was notable for microcytic anemia (Hemoglobin 91 g/L, MCV 75 fL), from a normal baseline one year prior, without other cytopenias. C-reactive protein (44 mg/L) and GGT (164 U/L) were elevated. Other liver enzymes, lactate dehydrogenase, and electrolytes were normal. Colonoscopy revealed numerous polypoid lesions throughout the entire colon and a large non-obstructive mass with submucosal appearance in the transverse colon. Biopsies were taken from the large mass and one of the smaller polypoid lesions. Histology showed a sheet-like infiltrate of small lymphocytes within the lamina propria. Immunohistochemical staining was positive for CD20, BCL2, Cyclin D1, equivocal for CD5, and negative for BCL6 and CD3. Ki67 index approached 30%. A diagnosis of colonic MCL was made. Literature Review Primary MCL of the GI tract is rare, accounting for only 1 to 4% of all GI malignancies. There is a male and Caucasian predominance with a median age of 68 years at diagnosis. Presenting complaints may include abdominal pain, anorexia, and GI bleeding. Typical endoscopic features are small nodular or polypoid tumors, between 2mm and 2 cm in size, along one or more segments of the GI tract referred to as multiple lymphomatous polyposis (MLP). A single colonic mass is infrequently seen, highlighting the importance of endoscopy for diagnosis, as subtle findings may be missed on radiographic evaluation. Biopsies for immunohistochemistry are essential to distinguish MCL from other NHLs, as almost all cases express cyclin D1. Despite aggressive immunochemotherapy, prognosis is often poor due to MCL’s rapid progression and early relapse. Conclusions Primary GI MCL is a rare entity. Awareness is essential as evaluation and management differ from lymphoma at other sites, and other GI malignancies. Funding Agencies None

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