ABSTRACT
The human breast, which at birth is a rudimentary bilateral organ, develops as the result of a combination of external and internal factors, all of which are intimately linked to the female reproductive system 1 . These factors, in turn, are modified by cultural, socioeconomic and environmental influences. Thus, in modern industrialized societies the fundamental role of the breast, nourishment of the offspring, becomes progressively less relevant, but at the same time this organ acquires new relevance because it constitutes the source of the most frequent malignancy in women. The higher risk of developing breast cancer has been associated with lengthened ovarian function, such as that occurring with early menarche and late menopause 2–8 . The increased risk associated with nulliparity or late first full-term pregnancy, or the protection afforded by early first full-term pregnancy are an indication that reproductive events, mainly through the hormonal influences of the new endocrine organ represented by the placenta, play important roles in modulating the susceptibility of the breast to undergo malignant transformation 1 .
