What this information really tries to determine is the likelihood that the woman has an abnormality in one of the breast cancer genes. If she doesn't, her risk is close to the general population. Two of these genes, called Br Ca 1 and Br Ca 2, are important in controlling cell growth and detecting cell abnormalities. Most women who develop breast cancer do not carry these genes. But, because breast cancer is so common, most women do have at least one relative who has had breast cancer.
Breast tissue begins developing before a baby is born.
Its growth is controlled by hormones. When children are small they produce very small amounts of these hormones and the breast grows very slowly. In boys and men the breast remains small in size. In girls, hormone production gradually increases during childhood and the breast begins to grow and develop into a more mature organ. At puberty, when girls begin to have menstrual periods, there are even higher amounts of hormones, especially estrogen and progesterone.