Resected cystadenoma of the common bile duct.

Biliary cystadenoma in the extrahepatic bile ducts is a very rare tumor. A 62-year-old woman with jaundice was admitted to our hospital. Imaging studies revealed a 4-cm cystic lesion around the hepatic hilum, compressing the common bile duct (CBD). When laparotomy was performed, a cystic tumor was detected in the hepatic hilum, filling the lumen of the CBD. Bile duct resection that included the tumor was performed, followed by biliary reconstruction. Microscopically, the cyst wall was lined by a single layer of cuboidal epithelial cells, covering an ovarian-like stroma. The degree of atypia was low and warranted the diagnosis of cystadenoma.