Mammary neoplasia in animals: pathologic aspects and the effects of contraceptive steroids.

Abstract

The incidence of spontaneous tumors of the mammary gland varies greatly among the different mammalian species. Large domesticated animals have a very low frequency of the disease. Even though the cow has enormous mammary gland development and cows numbering in the millions are observed to an old age, less than 50 cases have been reported in the literature. Similarly, mammary tumors are equally rare in sheep, horses, pigs, and goats. In contrast, the incidence of mammary tumors in the dog exceeds that of women by a factor of 3 to 4, and the disease is common in the cat. Rats and mice have a high incidence of mammary tumors; however, they are less frequent in other species of small laboratory animals. Mammary neoplasms are apparently rare in the nonhuman primate, but interest in the disease in these animals remains high as they have a menstrual cycle comparable to women. This paper reviews some major aspects of spontaneous mammary tumors in mice, rats, cats, dogs, and nonhuman primates. Emphasis has been placed on the pathologic aspects of the neoplasms and the use of these species in the carcinogenic testing of contraceptive steroids. The literature contains a large number of excellent publications on mammary neoplasia in animals; only selected articles are cited. The reader is especially referred to the comprehensive review by Hamilton published in 1974 [32] and the review by STEWART published in 1976 [68] on the comparative pathology of animal neoplasia.KeywordsMammary GlandMouse Mammary Tumor VirusTubular AdenocarcinomaMammary NoduleContraceptive SteroidThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.