A comparison of the histopathology of premalignant and malignant mammary gland lesions induced in sexually immature rats with those occurring in the human

The injection of sexually immature female rats with 1-methyl-1-nitrosourea results in a rapid induction of premalignant and malignant mammary gland le sions within 35 days of carcinogen administration. This model affords the o pportunity for investigators to study the process of mammary carcinogenesis over a very short latency and to investigate early events in this process. We have recently published on various aspects of this system including the histology of the lesions induced, the time frame of their occurrence, and their dependence on ovarian hormones for their maintenance and growth. In t his report we present evidence that many aspects of the histopathology of m ammary lesions in this model system are similar to those occurring in human s. We also discuss aspects of the human disease, which are not recapitulate d in this model.