Intraductal oncocytic papillary neoplasm of the extrahepatic biliary tree: first report.

Tumors with oncocytic differentiation may occur in a variety of organs, but are extremely rare in the biliary system. Intraductal oncocytic papillary neoplasms (IOPNs) were first described in the pancreas to differentiate a rare subset of pancreatic neoplasm from the intraductal papillary mucinous neoplasms (IPMNs). IOPN of the extrahepatic biliary tree has not been previously described.