S3452 Polypoid Puzzle: A Hidden Mucinous Biliary Cystadenoma Revealed in a Novel Fashion by Spyglass and ERCP Contrast Retention With Literature Review

Introduction: Biliary cystadenomas are rare, potentially malignant cystic neoplasms of the biliary ductal system accounting for a small portion of cystic lesions of the liver. While most cases are incidentally diagnosed on imaging, we present a unique case diagnosed via endoscopic retrograde cholangiopancreatography (ERCP) cholangioscopy (ERCP-C) finding a polypoid lesion within the bile duct and contrast retention within the cyst after ERCP-C. Case Description/Methods: A 59 year-old woman with intermittent episodes of epigastric pain for years developed acholic stools and dark urine. There was mild biliary dilation on ultrasound. Initial ERCP found small choledocholithiasis. Subsequent magnetic resonance imaging showed a 2.6 cm cyst in segment (seg) 4b of the liver (present on prior US), mild left intrahepatic duct dilation with narrowing just proximal to the right hepatic duct with a poorly defined 1.5 cm area noted. At that time, liver enzymes, CEA, and CA 19-9 were normal except mildly elevated alkaline phosphatase (123). Repeat ERCP-C was performed to rule out Klatskin tumor, revealing a 7 mm polypoid lesion originating from the distal left main hepatic duct. Biopsies showed benign biliary type epithelium. Subsequent cholecystectomy with common bile duct exploration showed a 4 cm polypoid lesion with the base in the left hepatic duct (LHD) and the free end prolapsing into the common hepatic duct (CHD), suggesting possible ball valve mechanism of biliary obstruction/injury. Pathology of the resection showed mucinous cystic neoplasm without evidence of high-grade dysplasia. Elevated CA 19-9 of 47.9 2 years later prompted an magnetic resonance imaging showing doubling of size in seg 4b cystic lesion to 2.7 × 1.9 cm. Repeat ERCP-C showed mild left biliary dilation and slightly delayed washout of contrast in seg 4b. Due to post-procedure pain, computed tomography showed retained ERCP contrast in a 3 cm cystic-solid mass, clearly indicating communication with the biliary tree. Left hepatic lobectomy was then performed with pathology showing a benign mucinous biliary cystadenoma of the liver with negative margins. Surveillance imaging over the following 2 years had no recurrence. Discussion: Most biliary cystadenomas manifest in middle aged women as a multilocular cystic mass, usually without biliary ductal communication per WHO criteria. Literature review revealed this to be the first noted report of a mucinous biliary cystadenoma in the liver initially presenting as a polypoid lesion seen on ERCP-C or as retained contrast after ERCP. Careful workup and ERCP-C are key to diagnosis.