The risk of developing breast cancer is higher among women whose close blood relatives have had this disease.

Having a mother, sister, or daughter with breast cancer doubles a woman's risk. Having two first-degree relatives with breast cancer increases the risk five-fold. According to the American Cancer Society, up to 10 percent of breast cancer cases are thought to be hereditary, resulting directly from gene mutations inherited from a parent.

For example, the BRCA genes (BRCA1 and BRCA2) are tumor suppressor genes. When mutated, they no longer suppress abnormal growth, and cancer is more likely to develop. Women with an inherited BRCA1 or BRCA2 mutation have up to an 80 percent chance of developing breast cancer during their lifetime, and when they do, it is often at a younger age than in women who are not born with one of these gene mutations.

Genetic testing is now possible, but not without complication or expense and is only recommended for about two percent of American women. Other controversial options for this high-risk group include chemotherapy-type medication or mastectomy as forms of prevention. High-risk women need to monitor changes in their breasts carefully to find cancer at an earlier, more treatable stage.