Rat models of premalignant breast disease

While a number of agents have been shown to induce mammary carcinogenesis i n the rat, premalignant stages of the disease have been best characterized in chemically-induced models, specifically those initiated by either 7,12 d imethylbenz[alpha ]anthracene (DMBA)(4) or 1-methyl-1-nitrosourea (MNU). In general, it appears that epithelial cells in mammary terminal end buds or terminal ductules are the targets of carcinogenic initiation, and that a se ries of morphologically identifiable steps are involved in the development of mammary carcinoma. The premalignant steps include ductal hyperplasia of the usual type and carcinoma in situ of the cribriform or comedo type; atyp ical ductal hyperplasia has not been reported. Thus the histogenesis of les ions occurring in chemically induced mammary carcinogenesis in the rat is s imilar to that observed in the human; although, the spectrum of lesions obs erved in the rat is limited. Opportunities to investigate the biological an d molecular characteristics of premalignant breast disease in the rat are p resented.