S3585 Pancreatic Head Mass With Jaundice: Not Always Pancreatic Adenocarcinoma—A Rare Case of Lymphoma Mimicking Pancreatic Adenocarcinoma

Introduction: Pancreatic head mass with biliary obstruction is most commonly associated with Pancreatic Adenocarcinoma (PAC). Pancreatic Primary Lymphomas (PPL) is a rare tumor that can also mimic this presentation. Accurate diagnosis through endoscopic intervention and histology is crucial in determining the appropriate therapy. Case Description/Methods: A 48-year-old man with no medical history presented with 3-month abdominal/back pain, scleral icterus, and pruritus without constitutional symptoms. Labs revealed cholestatic liver injury (ALP 455, AST 116, ALT 286) and elevated lipase (1,337). Right upper quadrant US showed a dilated common bile duct (1.9 cm) without intrahepatic biliary dilation. Computed tomography abdomen/pelvis revealed a 7.4 cm × 4.7 cm pancreatic head/uncinate process mass and a 2 cm × 2.3 cm mesenteric mass. Patient underwent endoscopic ultrasound (EUS) with fine needle aspiration (FNA) of the pancreatic mass and endoscopic retrograde cholangiopancreatography (ERCP) with biliary brushings, biliary sphincterotomy and stent placement due to biliary stricture. CA-199 and CEA were negative. Computed tomography abdomen 3 phase confirmed the pancreatic and mesenteric mass without vascular involvement. Computed tomography chest revealed no distant metastasis. Patient underwent computed tomography-guided biopsy of the mesenteric mass and internal jugular tunneled port placement for presumed PAC. The FNA was positive for B-cell lymphoma of follicle center cell origin, most likely follicular lymphoma or diffuse large B-cell lymphoma (DLBCL). Positron emission tomography scan showed a bulky lymph node with SUV >13 (16.3), concerning for aggressive lymphoma. R-CHOP was initiated to treat as aggressive B cell lymphoma. Discussion: PPL is a rare pancreatic tumor, representing 0.2% of all pancreatic tumors and the most common histological type is DLBCL (80%). PPL and PAC can be indistinguishable due to vague presentations of abdominal pain, jaundice, and constitutional symptoms and similar radiographic findings. Some studies suggest abdominal pain without jaundice or constitutional symptoms favors the diagnosis of PPLs. However, histological classification is require for a definitive diagnosis. Hence, endoscopic modalities like EUS-FNA are essential for diagnosis; and ERCP further allows for therapeutic intervention in cases of biliary obstruction or strictures. Distinguishing PPL from PAC is crucial because of the significant difference in management. PPL is treated with R-CHOP with possible radiation while PAC entails FOLFIRINOX and surgical resection, which alone carries serious risks including hemorrhage, pancreatitis, abscess formation, and anastomotic leak.