N-methylnitrosourea induced breast cancer in rat, the histopathology of the resulting tumours and its drawbacks as a model.

Several animal models of breast cancer have been developed to study various aspects of breast cancer biology. Substantial evidence suggests that the N-methylnitrosourea (MNU) animal model mimics human breast cancer in many respects. It has therefore been used extensively to evaluate preventive and therapeutic agents for human breast cancer. Chemically induced rodent models are also suitable for studying malignant progression. Recently, Liska et al. [7] established two protocols of MNU administration depending on the animal's age and number of applications of carcinogen, with the aim of investigating the advanced stages of mammary gland tumours. We used the same protocol as Liska but have obtained substantially different results. These results are presented and discussed in the frame of suggested key drawbacks of the MNU induced breast cancer rat model, as a contribution to the debate about the suitability of that model for evaluating preventive and therapeutic agents.