Hyperplastic polyp of the common bile duct.

We describe a hyperplastic polyp of the common bile duct, found in a 45-yr-old Japanese woman. Endoscopic retrograde sphincterotomy and intraductal biopsy yielded a histological diagnosis of adenocarcinoma, preoperatively. However, final diagnosis after pancreatoduodenectomy proved to be hyperplasia. The wrong diagnosis seemed attributable to tortuosity of the specimens caused by the biopsy procedure and/or a lack of experience of pathologists due to the rarity of this condition. One should be aware of this entity in diagnosing polypoid lesions in the biliary tract.