S3395 Primary Pancreatic Follicular Lymphoma: A Rare Incidental Finding During Evaluation for GI Bleeding

Introduction: Primary pancreatic follicular lymphoma (PPL) is an extremely rare form of extranodal non-Hodgkin lymphoma that originates in the pancreas. It accounts for less than 0.5% of pancreatic tumors and less than 1% of all extranodal lymphomas. Herein, we report a rare case of primary PPL discovered incidentally in a patient with symptomatic anemia. Case Description/Methods: A 65-year-old man with a history of type 2 diabetes presented to the ED with melena for 1 day. Triage labs: hemoglobin, 4.5 g/dL (reference range, 12.0-16.0), requiring 3 units of PRBCs. Computed tomography of the abdomen and pelvis revealed a thickened duodenum with air-fluid within it, suggestive of a duodenal ulcer. Esophagogastroduodenoscopy showed a gastric nodule, food residue, and a large, ulcerated, non-bleeding mass near the papilla. Colonoscopy was normal. Due to concern for ampullary mass, the patient underwent repeat EGD with endoscopic ultrasound (EUS) the next day. Endoscopic ultrasound (EUS) showed a mass in the uncinate process and fine-needle aspiration (FNA) was performed for histological analysis. EUS also showed a prominent ampulla and mucosal resection was performed for tissue sampling. Histopathology showed duodenal mucosa with acute and chronic inflammation, ulceration, and focal reactive changes. Endoscopic retrograde cholangiopancreatography (ERCP) revealed an ulcerated and mass-like lesion in the major papilla and a filling defect on cholangiogram, consistent with a stone. A biliary sphincterotomy was performed, and a covered metal stent was placed into the common bile duct. FNA specimen showed CD10 positive B-cell lymphoma, which was consistent with follicular lymphoma. B-cell lymphocytes stained positive for CD20, PAX-5, CD10, BCL-6, BCL-2, and Ki67 was approximately 30%. The patient was transitioned to hospice care after 6 cycles of obinutuzumab monotherapy. Discussion: Primary PPL is a rare but important diagnostic consideration in the evaluation of pancreatic masses. Cross-sectional imaging and tissue diagnosis with immunohistochemistry are key to differentiating lymphoma from more common pancreatic neoplasms. The primary treatment for PPL is systemic chemotherapy, often with regimens such as R-CHOP. CD20-targeting monoclonal antibodies can be considered in some cases. Surgery is generally reserved for diagnostic or palliative purposes rather than curative intent. Given the rarity of PPL, its management requires a high index of suspicion and a multidisciplinary approach to ensure timely and accurate diagnosis and appropriate treatment.