S4047 Colonoscopic Catfish: Follicular Lymphoma in Disguise

Introduction: Nodal follicular lymphoma is the most common sub-type of indolent Non-Hodgkins Lymphoma. However, primary gastrointestinal follicular lymphoma is exceedingly rare with an age-adjusted annual incidence of less than one percent. Clinical presentation is often vague or absent, and lesions are frequently discovered incidentally during endoscopic evaluation for unrelated symptoms. Here, we present a rare case of primary gastrointestinal follicular lymphoma incidentally diagnosed during routine screening colonoscopy. Case Description/Methods: A 54-year-old man presented for routine screening colonoscopy, with findings of a diminutive smooth sessile polyp in the rectum and 2 diminutive smooth sessile possible polyps vs lymphoid aggregates were found in the descending colon. All polyps were resected, and tissue was sent for biopsy. The terminal ileum appeared normal and was biopsied as well. All polyps and the terminal ileum were found to be positive for classic follicular lymphoma, with the cells positive for CD20, CD10, Bcl-6, and Bcl-2. A subsequent positron emission tomography-computed tomography (PET-CT) demonstrated a focally FDG avid mid-abdominal small bowel loop compatible with lymphoma involvement. While under surveillance, repeat PET-CT 5 months later demonstrated new focal activity in the left lateral pelvis corresponding to un-opacified loop of bowel with an interval decrease in activity in the mid abdominal bowel. There was also an increase in size, activity and extent of FDG avid mesenteric lymphadenopathy. Endoscopic ultrasound revealed small irregular hypoechoic nodes seen around stomach and duodenum in which FNA cytology was also positive for classic follicular lymphoma. Despite the imaging progression, the patient has been asymptomatic and is currently managed with active surveillance. Discussion: Primary gastrointestinal follicular lymphoma is generally asymptomatic and most commonly affects the duodenum with characteristic whitish polypoid or granular lesions. This case highlights the value of histologic sampling of even diminutive or ambiguous lesions, especially when there is uncertainty between polyp versus lymphoid aggregate. It emphasizes the importance of careful endoscopic evaluation and biopsy of even small or atypical lesions to ensure timely and accurate diagnosis.