About 20% to 30% of women with breast cancer have a family member with the disease. Women whose close relatives have breast cancer have a much higher risk of getting it. If a mother, sister or daughter has the disease, a woman has about double the risk. With two first-degree relatives with breast cancer, her risk increases five-fold, according to the American Cancer Society.
A woman whose father or brother has breast cancer also has an increased risk, but exact risk has not been established.
There is some good news for women saddled with a family history: A recent study in the Archives of Internal Medicine found that among women whose mothers or sisters had breast cancer, those who breast-fed had a 59% lower risk of breast cancer compared with women who had never breast-fed. Breast-feeding was comparable in lowering risk to taking the estrogen-blocking drug Tamoxifen for five years, the study authors said.
If you do have breast cancer in your family history, talk with your doctor to see whether you may need earlier and more frequent screening or genetic testing.