Abstract
This review focuses on the comparative aspects of chemical carcinogenesis in the two major rodent species, rat and mouse, that have been used for the past 50 years. The areas discussed are the similarities and differences in mammary tumorigenesis in response to similar chemical carcinogens, the strengths and weaknesses of each model and the usefulness of each model for understanding the cellular and molecular basis in the development and pathology of human breast cancer. Human breast cancer is a very heterogeneous disease and presents itself in many forms. One important lesson derived from the use of animal models is that each model serves to illuminate some aspect of human breast cancer and mimics a subset of the many subsets of human breast disease. Thus, many different models will be needed to fully enable an understanding of the cellular and molecular basis for human breast cancer and eventually provide the critical preventive and therapeutic approaches to conquer this cancer.