A mixed hepatocellular carcinoma and cholangiocarcinoma: dual expression of biliary-type cytokeratin and hepatocyte specific marker.

A 5-cm lesion in the right hepatic lobe was detected in a 61-year-old man with chronic hepatitis C by ultrasonography. Contrast-enhanced computed tomography showed a low-density lesion with wide peripheral enhancement. Hepatic angiography revealed that the tumor had partial hypervascularity. Although serum concentrations of alpha-fetoprotein and carcinoembryonic antigen were within normal limits, an elevated concentration of carcinohydrate antigen 19-9 was detected in serum. A definitive diagnosis was not made although we strongly suspected mixed hepatocellular carcinoma and cholangiocarcinoma. Since intraoperative frozen-section examination revealed adenocarcinoma, a right hepatic lobectomy with regional lymph node dissection was performed. A histologic diagnosis of mixed hepatocellular carcinoma and cholangiocarcinoma was made because the hepatic tumor consisted of components of both hepatocellular carcinoma and cholangiocellular carcinoma, with a transitional area. Additionally, immunohistochemical examination revealed that some tumor cells in the transitional area were immunoreactive for both cytokeratin 19 and hepatocyte paraffin 1.