Cholangiolocellular carcinoma: an innocent-looking malignant liver tumor mimicking ductular reaction.

The authors present an interesting case of a 60-year-old man who underwent right hepatectomy for a diagnosis of hepatocellular carcinoma (HCC) on a background of noncirrhotic chronic hepatitis C. Pathologic examination confirmed the presence of HCC near the porta hepatis, which invaded the right portal vein branch. In addition, a well-demarcated 13.5 × 7.8 × 4.0 cm yellow and firm area upstream of the HCC was noted. This yellow area corresponded to a tumoral ductular proliferation, which cytologically was extremely bland, but invaded portal tracts and the adjacent liver parenchyma. This tumoral proliferation mimicked ductular reaction, except that it had more anastomosing structures and was associated with abundant hyalinized fibrotic stroma. Cytologically, the tumor cells had round to oval nuclei with fine chromatin, indistinct nucleoli, and scant cytoplasm. They exhibited immunohistochemical features of hepatic progenitor cells, i.e., expressing CK7, CK19, and N-CAM; and their malignancy was supported by the p53 and Ki67 immunoreactivity. The authors concluded that the patient had cholangiolocellular carcinoma with an aggressive hepatocellular carcinoma component. Cholangiolocellular carcinoma has been reported to be associated with chronic hepatitis C viral infection and to derive from hepatic progenitor cells, which explains why hepatocellular carcinoma and/or cholangiocarcinoma component may be present.