HCC is not a major killer among malignant diseases in Western countries, and until recently few Western hepatologists were interested in this cancer. After the demonstration of an etiologic role for HBV infection in hepatocarcinogenesis, interest surged even in lowincidence countries, particularly among molecular biologists and oncologists. A large body of literature now exists dealing with molecular mechanism in HBVrelated human HCC and hepadnavirus-induced HCC in animals. The recent identification and cloning of hepatitis C virus (HCV) has focused interest on chronic C hepatitis which, under the name of non-A, non-B (NANB) hepatitis, had for some time been suspected as another etiological factor for HCC in certain areas of the world. It did not take long before well-documented evidence linked HCV to HCC. Imaging diagnosis of small-mass lesions in the liver has progressed remarkably in recent years, as emphasized in a previous review in this JOURNAL (1). In countries where detection and resection of small HCCs in cirrhotic livers are common practice, pathologists are discussing how to differentiate large, benign, hyperplastic nodules; adenomatous hyperplastic nodules with potential to transform; and early HCC lesions histopathologically. Radiologists are attempting to make similar diagnostic distinction by imaging alone with limited success. This review attempts to update the recent progress made in the basic study of HCC.
EPIDEMIOLOGY AND ETIOLOGYAccording to Muiioz and Bosch (2), no clear indication of a change has appeared in the incidence rate of HCC in developed Western countries in the past 20 yr or so as far as cancer registry data are concerned. However, in Japan, incidence of HCC began to increase about 20 yr ago; the increase was accounted for by non-HBV-related cases, and an etiologic role of chronic NANB hepatitis was suspected in the early 1980s (3). All cancer registries in Japan have clearly shown significant increases in HCC because of non-HBV-related cases. HBsAgpositive patients accounted for more than 40% of all HCC cases in the early 1970s, when testing was by the immunoprecipitation techniques. This figure is currently less than 20% as tested by the much more sensitive methods (4). At the autopsy table, the numbers of patients with HCC and of those with cirrhosis alone were about the same in early 1960s, but HCC now far exceeds cirrhosis in number. The frequency of complicating HCC among all cirrhotic livers autopsied used to be 20% to 40% and is currently about 80% (5). A similar trend of increase has been observed among autopsies in northern Italy (6) and the United States (7). A number of studies in Japan have shown that the frequency with which HCC develops in cirrhotic patients during follow-up is more than 6%/yr (8) among all cirrhotic patients. In a recent study in northern Italy, HCC developed in 29 (7%) of 417 patients with cirrhosis (62% viral) during follow-up periods averaging 33 mo (9).Shortly after the identification of HCV by the group at Chiron Laboratories and the developmen...