S1581 Ampullary Adenocarcinoma Mimicking Annular Pancreas on Imaging

Abstract

INTRODUCTION: Ampullary adenocarcinoma is a rare malignant tumor that accounts for 0.2% of all gastrointestinal malignancies. It arises in the ampulla just distal to the confluence of the common bile duct and the pancreatic duct. In the literature, there are many reported cases of non-malignant mimickers that can appear as adenocarcinomas on imaging, such as annular pancreas and cystic tumors. However, to our knowledge, there are no reports of an ampullary tumor that mimics annular pancreas on computed tomography (CT) which we will present in our case. CASE DESCRIPTION/METHODS: 67 years old Male who is a former smoker and heavy alcohol consumer who presented with abdominal pain, distention, weight loss and constipation, CT abdomen revealed a multicystic mass surrounding second part of duodenum. An endoscopic ultrasound with fine needle aspiration (EUS-FNA) showed an anechoic 3.3 × 2cm multicystic lesion in pancreatic head. Carcinoembryonic antigen was markedly elevated (CEA 575) in cystic fluid and cytology revealed adenocarcinoma. A Whipple surgery was done and pathologic evaluation revealed ampullary adenocarcinoma with pancreaticobiliary origin invading superficially into pancreatic and periduodenal tissue with peripancreatic and periesophageal lymph nodes involvement. DISCUSSION: Several inflammatory, cystic tumors and congenital variants (ex, annular pancreas) can mimic pancreatic ductal adenocarcinoma appearance on imaging but no previously reported tumor mimicked annular pancreas on different imaging modalities. Therefore, in appropriate clinical setting, a finding of an annular pancreas on imaging might require further workup with EUS-FNA to exclude malignant lesions.Figure 1.: Multicystic mass surrounding the second part of duodenum correlating with an annular pancreas.Figure 2.: Multi-cystic lesion seen on endoscopic ultrasound.Figure 3.: Severe stenosis in second part of the duodenum seen on Endoscopy.