Examination of three strains of inbred mice suggested that specific morphological types of hepatic tumors are the result of genetic predisposition while other type of tumors are associated with exposure to chemical carcinogens. A simple classification system is proposed. Additional studies indicated that a putative promoting agent, such as phenobarbital, increased the incidence of those tumor types usually associated with spontaneous appearance and only in strains with a genetic predisposition to spontaneous tumorigenesis. Carcinogens induce an increase in all types of tumors.

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This investigation was supported in part by Contact CP65846 and Grant CA20659 awarded by the National Cancer Institute, Department of Health and Human Services. This was presented in part at the CIIT Conference, “Current Perspectives in Mouse Liver Neoplasia,” December 4, 1981, Raleigh, N. C.

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