Hepatocellular carcinoma--a model of human cancer: clinico-pathological features, etiology and pathogenesis

Hepatocellular carcinoma (HCC), a unique human neoplasm, has interested many in several fields of biological and health sciences. This cancer is credited as the first that can be largely eliminated by a safe anti-viral vaccine and other transmission control measures. It is also the first cancer for which a reliable diagnostic tumour marker was identified and studies on this tumor in humans and animals have provided a large body of information on causation and step-wise evolution of cancers. Being a common and rapidly fatal tumour, mainly affecting males in the more populous developing countries, HCC may well be the commonest cancer of the human male. Clinical features are not specific for HCC but manifestations represent varying combinations of those due to cirrhosis which is a very frequently associated and pre-existent disease, those due to tumour and those due to malignancy. This tumour commonly takes a massive form with satellite nodules or a scattered multinodular form. A fibrolamellar variant is biologically and clinically quite different from the usual HCC and the small capsulated variant is seen in some geographic areas. Microscopically the trabecular variety is common and differentiation from metastatic cancers and benign lesions may need use of newly described immunohistochemical markers in addition to clinical evidence of cirrhosis. Hepatitis B and C viruses, dietary aflatoxin B1 and cirrhosis from any cause are common risk factors in that order of importance. Several lines of evidence including molecular biology and animal studies support these etiological linkages. Studies in experimental animals using chemical carcinogens, different hepatotropic viruses and aflatoxin have greatly helped our understanding of carcinogenesis in general and hepatocarcinogenesis in particular. Individual HCC risk factors may contribute to summation of mutations subsequent to repeated and continued liver cell injury act as carcinogen/co-carcinogen or be involved in both capacities.