Pathology of early hepatocellular carcinoma.

As is observed in many types of human cancers, hepatocellular carcinoma (HCC) is characterized by an obvious multistage process of tumor progression. Histopathological and molecular biological studies have revealed that HCC associated with chronic liver disease evolves from precancerous lesions called adenomatous hyperplasia (also called dysplastic nodules) and early HCC to a progressed form. Early HCC corresponds to in situ or microinvasive carcinoma, and develops to progressed HCC through the stage of "nodule-in-nodule" type HCC (progressed HCC within early HCC), which indicates a transition from early to progressed HCC. It is consideredthat early HCC is a key step in the process of HCC development and progression. However, the molecular mechanisms of early hepatocarcinogenesis are far from clear. Specific mutations of classical oncogenes or tumor suppressor genes have not been identified in early HCC so far. Recent progress in comprehensive analysis of gene expression is shedding some light on this issue.