[Breast density: a major parameter to follow during hormone replacement therapy]

Mammographic density is a risk factor for breast cancer and it reflects variations in the tissue composition of the breast. It is notably influenced by body mass index and by endogenous hormones as well as hormone replacement therapy (HRT). The pathways that are responsible for the increase in mammographic density following exposure to hormones and those that increase risk of breast cancer are probably not the same. Careful clinical and mammographic follow-up is appropriate in women undergoing HRT because an increase in density is not only a risk factor for breast cancer but it also reduces screening sensitivity. We present a case in which mammographic density decreased after menopause, then dramatically increased after HRT and finally, surgical biopsy allowed the diagnosis of an infiltrative breast carcinoma. We discuss appropriate HRT changes in case of increasing mammographic density.