ABSTRACT
Analysis of experimental liver carcinogenesis is an old research theme dating back to early successful attempts to induce hepatocellular carcinomas with a variety of chemicals in rats (1). Subsequent studies revealed that focal populations with an aberrant phenotypic expression may be preneoplastic in character, and several trials have been performed to classify preneoplastic and neoplastic lesions. The mor phological sequence of events in liver cancer pathogenesis may be similar in all animal species studied. However, specific differences in the histogenesis and mor phology of tumors between strains of a given species and between species have been found. A discussion of the terminology and diagnosis of hepatoproliferative lesions should therefore also be prefaced by an explanation of the diagnostic process. In this chapter we review histopathologic typing of proliferating lesions of the rat liver, their characteristics, and their usefulness in risk assessment.
