Classification of premalignant and malignant lesions developing in the rat mammary gland after injection of sexually immature rats with 1-methyl-1-nitrosourea

Abstract

Premalignant and malignant stages of mammary carcinogenesis can be rapidly induced by injecting female rats i.p. with 1-methyl-1-nitrosourea (MNU)3 at 21 days of age. In this paper, the characteristics of this model are briefly reviewed and the histology of the lesions induced is presented and compared to those that occur in humans. Malignant mammary lesions induced in rats injected with MNU at 21 days of age are compared with the lesions that develop when MNU is administered to 50-day-old female rats.