[Breast cancer, model in biological and clinical oncology. Role of hormones and growth factors].

It is shown that breast cancer can be considered as a paradigm of comprehensive cancer biology and treatment based on analysis of each individual tumor. Historically, it was first observed in breast cancer that tumor progression could be dependent on factors regulating physiological activities (i.e. hormones). It was also observed that tumor growth progressively becomes autonomous, through successive degradation of the multiple steps involved in the control of cell proliferation and differentiated activities. Hormonal treatment of breast cancer provided the first example of targetted biotherapy. The discovery of the mechanism of action of hormones via specific receptors opened the field of tumor tissue analysis to determine the main biological factors involved in tumor progression. In the near future, such data should be the best guide for selection of the most appropriate treatment in each individual case.