Successful preoperative diagnosis of biliary cystadenoma with mesenchymal stroma and its characteristic imaging features: report of two cases.

We report two cases of biliary cystadenoma with mesenchymal stroma, in which we reached a preoperative diagnosis. There are three characteristics in imaging. First, there is no communication between the tumors and biliary ducts. Second, the wall of the tumor is smooth and septa inside the tumor result in a 'cysts-in-cyst' appearance. Third, papillary projections that are characteristic of the intraductal papillary mucinous neoplasm of the bile duct are rarely seen. We provide characteristic figures that are remarkably helpful for the preoperative diagnosis.