Introduction: Primary gastrointestinal(GI) mantle cell lymphoma (MCL) is a rare and aggressive malignancy. Endoscopy typically shows multiple lymphomatous polyposis (MLP) but other findings have been reported. We describe a case of primary GI MCL diagnosed during routine colon cancer screening. Case: A 61-year-old Hispanic female presented for a routine colonoscopy. Fifteen years prior, she underwent colonoscopy with polypectomy in El Salvador; report was not available. She denied fevers, chills, weight loss, diaphoresis, abdominal pain, melena, and hematochezia. Abdominal exam was benign and without lymphadenopathy. On colonoscopy, 3 sigmoidal polyps- all less than 5mm- were resected; the remaining mucosa was normal in appearance. Histology for 2 of the polyps showed lymphoid infiltrate with CD20+ B cells, reactive germinal centers, and expanded mantle zones, consistent with mantle cell lymphoma. The third polyp was an adenoma. Patient was referred to oncology and a workup of CT scans, FDG-PET CT, bone marrow biopsy and flow cytometry were normal. Patient declined chemotherapy and was observed. A colonoscopy 3 months later showed normal-appearing mucosa but biopsies from each colonic segment demonstrated diffuse MCL. Discussion: Primary GI MCL accounts for 1-4% of all GI lymphomas. The most common endoscopic finding is intestinal MLP but previous cases report ulcerated lesions, mucosal color changes or thickening, and frank masses. Our patient only had 3 small polyps on the initial screening and normal-appearing mucosa on the repeat endoscopy. Microscopic evidence of MCL is actually seen in two-thirds of cases with endoscopically normal mucosa but the significance of this on patient outcome is unclear. Primary GI MCL is often diagnosed in end stages and has a poor prognosis but the median survival remains to be studied. Chemotherapy regimens such as CHOP achieved high remission rates but for short time periods. More recently, the hyper-CVAD/MA regimen with rituximab has been established as an effective cytoreductive regimen with a high response rate. Our patient was offered bendamustine and rituximab, an effective regimen often utilized in older MCL patients. Specific regimens vary based on disease severity and patient's functional status. This case highlights an atypical presentation of a rare malignancy, the importance of timely screening colonoscopies, and the consideration of performing random colon biopsies on patients with MCL polyp pathology.