Most people who develop breast cancer have no family history of the disease. However, if you do have a family history of breast cancer, ovarian cancer, or both, heredity could have played a role in the cancer’s development. Most inherited cases of breast cancer are associated with two abnormal genes: BRCA1 (BReast CAncer gene 1) or BRCA2 (BReast CAncer gene 2). Women who inherit a mutation, or abnormal change, in either of these genes — from their mothers or their fathers — have a much higher-than-average lifetime risk of developing breast cancer and ovarian cancer.
Genetic testing for BRCA1 and BRCA2 is NOT part of the standard pathology workup. Finding out whether you have an inherited gene abnormality requires a special test that uses a blood sample, not a tissue sample. If your doctor is concerned that you and your immediate relatives may have an inherited gene abnormality, he or she may recommend that you and other family members be tested.
According to the National Cancer Institute, women with an abnormal BRCA1 or BRCA2 gene have about a 60% risk of being diagnosed with breast cancer during their lifetimes (compared to 12-13% for women overall). These women’s risk of ovarian cancer is also increased. Abnormal BRCA1 or BRCA2 genes are found in 5-10% of all breast cancer cases in the United States. Other types of inherited gene abnormalities are less common.
Learn more about BRCA1 and BRCA2 (genetic) testing.
Simply having a proven gene abnormality does not necessarily mean that a woman will develop breast cancer, or that her cancer will be any worse than cancer that does not stem from an inherited genetic flaw.