Background: p63 helps regulate differentiation and proliferation in epithelial progenitor cells. Its expression is often higher in malignant tissue compared with normal tissue, and poorly differentiated carcinomas often show a larger number of p63-positive cells than well-differentiated tumors. The aim of the present study was to investigate the immunohistochemical expression of p63 in human cholangiocarcinomas (CC) and hepatocellular carcinomas (HCC).
Methods: Sixteen cases of CC and 37 cases of HCC were selected for the present study. Paraffin-embedded sections were submitted to immunohistochemical double-staining to identify p63 and cytokeratin 19.
Results: p63 was diffusely expressed in 100% of CC, while it was negative in all HCC. In addition, cytokeratin 19, a marker for hepatic progenitor cells, was colocalized in all p63-positive cells.
Conclusions: The nuclear immunostaining for p63 in all CC cases indicates that the p63 protein can act to promote neoplastic growth in bile duct epithelium, but it is not important for hepatocellular carcinogenesis. Co-localization of p63 and cytokeratin 19 in CC cells suggests that CC may be derived from undifferentiated progenitor cells (hepatic oval cells). Furthermore, p63 can be useful in the differential diagnosis between CC and HCC in biopsy samples.