Unusual cause of a polypoid lesion in the extrahepatic bile duct

Adenomyomas are benign lesions that are most frequently found in the gallbladder but can also be rarely found in the biliary tract. Although benign, they present close similarity to malignant lesions and thus deserve important clinical consideration. We present a case of a 74‐year‐old Chinese man who presented acutely with fever and painless obstructive jaundice. CT imaging showed a large calculus within a dilated common bile duct (CBD) and, despite undergoing an endoscopic retrograde cholangiopancreatography (ERCP) with stone clearance, there was a persistent filling defect that was adherent to the wall of the proximal common bile duct. His CA 19–9 was also significantly raised. Intraductal ultrasonography (IDUS) showed a polypoid mass with papillary‐like projections, and ERCP forcep biopsies were unable to exclude a lesion with neoplastic potential. The patient subsequently underwent cholecystectomy with open CBD excision and Roux‐en‐Y hepaticojejunostomy, and histology showed features consistent with a biliary adenomyoma.