S1493 A Benign Common Bile Duct Tumor: A Diagnostic Dilemma

Abstract

Introduction: Benign extrahepatic bile duct tumors are uncommon, accounting for 6% of all extrahepatic bile duct masses. They tend to occur later in life and can present early with obstructive jaundice. They are morphologically and histologically similar with each other which makes it challenging to make an accurate diagnosis. These lesions can progress to malignancy so timely diagnosis and appropriate treatment is critical. We present a case of a benign common bile duct (CBD) tumor presenting in a healthy young man that had both features of a papillary and a tubulo-villous neoplasia, causing a diagnostic dilemma. Case Description/Methods: Patient is a 48-year-old man with history of pancreatic DB-IPMN, presenting with a one-month history of post-prandial upper abdominal pain. Physical exam was unremarkable. Labs showed elevated liver enzymes with ALT, AST, and ALP of 186, 78 U/L, 537 U/L, respectively; total bilirubin was 1 mg/dL. Abdominal MRI showed diffuse dilation of intrahepatic and extrahepatic ducts, as well as dilation of the pancreas duct with a prominent ampulla. ERCP showed a bulging ampulla with abnormal appearing tissue in the distal CBD [Figure 1]. Biopsy of the of distal CBD revealed intra-papillary neoplasm of bile duct (IPNB) without features of high-grade dysplasia [Figure 2A]. A fully covered metal stent was placed with immediate improvement in symptoms and laboratory markers. Case reviewed in tumor board which recommended obtaining more tissue prior to definitive management. A repeat ERCP with SpyGlass cholangioscopy-directed biopsies and biopsies of the ampulla revealed tubule-villous adenoma with high grade dysplasia [Figure 2B]. The patient underwent curative pancreaticoduodenectomy. Final histology did not reveal invasive cancer. Discussion: IPNB is an uncommon benign extra-hepatic bile duct tumor, characterized by papillary or villous growth within the bile duct lumen. It is more common in elderly men and can progress from atypia to invasive cholangiocarcinoma. About half of IPNBs show stromal invasion at the time of surgical resection. Accurate and timely diagnosis before metastasis is critical as surgical resection has excellent outcome with 5-year tumor free survival being 80%. Our case highlights an IPNB of the distal CBD extending into the ampulla, masquerading as a more common adenoma of the duodenal ampulla.Figure 1.: ERCP showing prominent ampulla (1a) and biliary sphincterotomy (1b)Figure 2.: Figure 2A: (Biospy#1) Intraductal papillary Neoplasia (papillary proliferation of biliary epithelium along with delicate fibrovascular cores) Figure 2B: (Biospy#2) (a) At low power (40x) demonstrating tubulovillous adenoma with papillary features. Figure 2B: (Biospy#2) (b) At high power (400x) showing an area with high grade dysplasia with cribriforming, nuclear atypia, and abundant mitotic figures.