Multidisciplinary Approach to a Challenging Diagnosis of a Pancreatic Intraductal Neoplasm in the Ampulla of Vater

Introduction: Intraductal papillary mucinous neoplasms (IPMNs) are tumors that grow within the pancreatic duct. They are known as the most common pancreatic cystic neoplasm that are likely to progress to malignancy. The location associated with the highest risk of malignancy is within the main pancreatic duct. The majority of these tumors are asymptomatic, but they can cause jaundice or stomach pain. We present a unique case of an IPMN that invaded the ampulla of Vater and resembled a primary ampullary mass. Few case reports have shown such a diagnostic challenge of identifying an IPMN which was so enlarged that it masqueraded as an enlarged ampullary mass causing biliary duct dilation. Case Description/Methods: A 54-year-old male with a history of chronic pancreatitis and pancreatic divisum presented for evaluation of abdominal pain, jaundice, and dark urine. Physical exam was significant for scleral icterus. Labwork revealed a total bilirubin of 8.6, direct bilirubin of 4.8, alkaline phosphatase of 842, AST of 129, and ALT of 218. Ultrasound revealed a dilated pancreatic duct with a possible distal CBD stricture or pancreatic duct stricture. Patient was then scheduled for an Endoscopic Ultrasound (EUS) and ERCP. The EUS revealed a parenchymal mass and an ampullary mass at the head of the pancreas. ERCP showed a filling defect at the distal common bile stricture and a metallic stent was placed. The ampullary mass was then biopsied and pathology results revealed moderately differentiated adenocarcinoma of the pancreas. The patient ultimately underwent a pylorus pancreaticoduodenectomy and surgical pathology revealed moderately differentiated mucinous adenocarcinoma, arising from a main duct intraductal papillary mucinous neoplasm. The tumor had invaded the head of the pancreas and extended into the ampulla (Figure 1). Discussion: We present a rare case of IPMN protruding through the ampulla of the Vater. Initially it was misidentified and our case highlights the difficulty of differentiating between an ampullary tubulovillous adenoma and a papillary mucinous tumor. Usually, Endoscopic treatment helps assess and locate the lesion to help minimize surgery. However, this case required a larger pathologic sample of the tumor to confirm diagnosis of IPMN via a pancreaticoduodenectomy. Despite endoscopic advancement, it can still be difficult to identify ampullary adenomas further supporting the importance of a strong differential diagnosis and multidisciplinary approach.Figure 1.: An ampullary mass is seen on ERCP, later identified to be an enlarging IPMN.