ABSTRACT
There are a number of reasons for the widespread use of laboratory mice and rats in breast cancer research. This chapter discusses the characteristics of preneoplastic mammary hyperplastic alveolar nodules (HAN) and spontaneous mammary tumors of mice, an “ex-vivo in-vivo” system in athymic nude mice, and spontaneous, carcinogen- or radiation-induced mammary tumors of rats. While HAN differs little morphologically from normal lobulo-alveoli, the response of the former to Prolactin (PRL) is much greater than that of the latter. While mammary tumors develop spontaneously in rats, there are striking differences in mammary tumorigenic potential between rat strains. An important role for PRL in mammary tumorigenesis in mice and rats is overwhelmingly supported by an array of laboratory studies. PRL is also important in the development of spontaneous mammary tumors in female rats, a phenomenon that also appears to be related to the mitogenic activities of this pituitary peptide on the normal mammary epithelium.
