Abstract
A 56 year old man was admitted to our hospital with complaints of jaundice and fever. Abdominal ultrasonography revealed slight dilatation of the common bile duct (CBD) . A stone in the CBD, a tumor in the distal CBD, and a choledocho duodenal fistula were revealed by choledochocystography. Examination of an endoscopic biopsy specimen revealed a papillary adenoma. A specimen obtained at pancreatoduodenectomy contained a papillary tumor of the lower CBD and a choledocho duodenal fistula. Histologic examination revealed adenocarcinoma in adenoma. This case illustrates the malignant potential of adenoma in the biliary tract.