[Progesterone and breast cancer].

In Western countries the carcinoma of the breast has an incidence of 45 cases on 1000 women. Much clinical and epidemiological evidence demonstrates that all the conditions of hyperestrogenism and extended exposure to estrogens are associated with increased incidence of malignant mammary epithelial tumor. The relationship between the exposure to ovarian hormones and mammary neoplasia has created doubts about using hormone substitution therapy in menopause. Through an analysis of the recent literature our work aims to evaluate the action of progesterone on the breast and, in particular, to study its effects on the cells of the mammary gland in association to estrogens during hormone replacement therapy in menopause.