CYP2D6 and hepatocellular carcinoma: Our previous systematic studies on 10 major CYP enzymes responsible for hepatic drug metabolism showed significant changes in CYP polymorphism incidence [10] and enzyme activity [13–15] in HCC patients, some of which were confirmed as related to increased susceptibility to hepatofibrosis and HCC [16, 17], especially for increased activity of CYP2D6 and CYP2E1, decreased activity of CYP2C8, and decreased frequency of the CYP2D6*2 allele.