[Hepatitis B and C viruses and primary liver cancer].

Chronic infections by hepatitis B and C viruses are major risk factors for primary liver cancer. In both infections, induction of chronic active hepatitis followed by cirrhosis precedes development of the tumor and is a major mechanism of liver carcinogenesis. For hepatitis B virus, several elements indicate that the virus might also exert direct effects through cis and transactivation of cellular genes. For hepatitis C virus, such a direct effect has not yet been demonstrated.