Most women who are diagnosed
with breast cancer do not have
a family history of the disease.
Over 75% of the women who have breast cancer have no relatives with the disease.
However, having one or more relatives who have had breast cancer does increase your risk. We have discovered that, among some women with a significant family history, certain inherited mutations of the genes BRCA 1 and BRCA 2, found in about 5-10 percent of all breast cancer cases, may result in an even higher risk of breast cancer. The mutations are sometimes (but not always) passed down to relatives. Less than 10% of women with breast cancer have a known gene mutation that increases risk, which is often referred to as genetic predisposition. Not everyone with a family history has a known gene mutation.
A family history is one risk factor. But a risk factor doesn't cause cancer; it just affects your chance of getting cancer. Other risk factors for breast cancer include getting older, benign breast problems, early exposure to ionizing radiation, having children late in life or not at all, longer exposure to estrogen and progesterone, lack of exercise, and drinking alcohol.