Breast Cancer 101 - Breast Anatomy

Development
Although most people don't think about it, both men and women have breasts. Breast development starts before you are born. A mammary ridge or the milk line develops in the fetus at about six weeks. It stretches to the groin area and then becomes more localized and changes into recognizable breasts as it matures.

When fully developed the breast tissue covers from the second rib to the sixth rib starting at the edge of the sternum - your breast bone, and reaching to the side of your body. If you draw a line from the middle of your underarm downwards, that line would mark the end of the breast tissue.

Earliest Stages
Although most babies are born with normal breasts, occasionally there will be a birth defect. This is usually an extra or a missing nipple on one or both breasts, or extra breast tissue. A missing nipple can be corrected cosmetically with plastic surgery. Extra nipples, polythelia, are usually mistaken as moles and unless a problem develops, this condition is usually just ignored. Oddly enough, although extra nipples only occur in one to five percent of newborns, they are more common in males.

Extra breast tissue which is called polymastia, does not usually cause a problem. It may produce small lumps on the chest or under the arms. However, this extra tissue can develop the same problems as normal breasts. Cysts, fibroid tumors and even cancer can occur in this misplaced tissue. These conditions are rare and should not be a cause for concern unless you have been told by your doctor that you have them. Removal of this tissue is not encouraged because surgery in the area can damage the structures that make up the breast and interfere with normal lactation.

In the uterus, estrogen from the mother's body affects the babies breasts. Full term infants of both sexes have noticeable amounts of breast tissue. These "breast buds" normally disappear by six months. Discharge from the breasts of babies, both boys and girls, is common.

Normally, during childhood the breasts are flat and there are no signs of development. The breasts of boys and girls are similar.

Breast cancer has been recorded in girls as young as five, but this is so rare that for statistical purposes the American Cancer Society does not recognize any risk until a woman is 20. Age risks for men have not been calculated.