S5287 An Unusual Presentation of Diffuse Large B-Cell Lymphoma With Pancreatic Involvement: Diagnostic Utility of Endoscopic Ultrasound in Staging and Detection

Introduction: Primary pancreatic lymphoma is an uncommon extranodal manifestation of non-Hodgkin lymphoma and accounts for less than 0.5 percent of pancreatic malignancies. Diffuse large B-cell lymphoma (DLBCL) is the most common histologic subtype, but pancreatic involvement, whether primary or secondary, is rare. Clinical and radiographic features often resemble pancreatic adenocarcinoma, making histologic confirmation essential. Endoscopic ultrasound with fine-needle biopsy plays a critical role in characterizing deep lesions, guiding diagnosis, and informing management. Case Description: An 83-year-old man with a history of hypertension, hyperlipidemia, gastroesophageal reflux disease, and hypothyroidism underwent upper endoscopy for evaluation of dyspepsia. Esophagogastroduodenoscopy revealed a suspicious gastric ulcer. Initial biopsies were nondiagnostic. He was referred for an endoscopic ultrasound (EUS), which identified a submucosal mass with hypoechoic features. Fine-needle biopsy revealed high-grade B-cell lymphoma consistent with gastric DLBCL. PET scan performed for staging demonstrated hypermetabolic activity in the pancreas that was concerning for secondary involvement. Repeat EUS targeted towards the pancreatic lesion with fine needle biopsy confirming DLBCL of the pancreas. Immunohistochemistry was positive for CD20 and showed a high proliferative index with Ki-67. The patient was diagnosed with stage intravenous lymphoma and referred to oncology for systemic chemotherapy. Discussion: This case illustrates a rare presentation of DLBCL involving both the stomach and pancreas. The pancreas is an atypical site for lymphoma and its involvement may be radiographically indistinguishable from pancreatic adenocarcinoma. Histologic confirmation with EUS-guided biopsy was essential to establish the diagnosis, avoid unnecessary surgical intervention, and initiate appropriate treatment. In patients with upper gastrointestinal abnormalities and concurrent imaging findings suggestive of a pancreatic mass, endoscopic ultrasound should be considered to distinguish hematologic from epithelial malignancies. This case underscores the importance of endoscopic ultrasound in both diagnosis and staging of extranodal lymphomas presenting in unusual anatomic locations.