The breast cancer 1 (BRCA1) and breast cancer 2 (BRCA2) genes are the genes most commonly affected in hereditary breast and ovarian cancer. Normally, the BRCA1 and BRCA2 genes protect you from getting certain cancers. But certain mutations in the BRCA1 and BRCA2 genes prevent them from working properly, so that if you inherit one of these mutations, you are more likely to get breast, ovarian, and other cancers. You and your family members are more likely to have a BRCA1 or BRCA2 mutation if your family has a strong history of breast or ovarian cancer. Because BRCA1 and BRCA2 mutations are inherited, family members with BRCA1 or BRCA2 mutations usually share the same mutation.
Having a strong family health history of breast and ovarian cancer does not mean that you definitely have an inherited mutation. In fact, most women identified as being at increased risk for BRCA1 and BRCA2 mutations based on family health history do not have BRCA1 or BRCA2 mutations.
Using family health history information will not find everyone with BRCA1 or BRCA2 mutations. Not everyone with a BRCA1 or BRCA2 mutation has a strong family health history of breast and ovarian cancer. Some even have no known family health history of breast and ovarian cancer.
The bottom line is that if you have a family member or members who have had breast or ovarian cancer, it is in your best interest to have genetic testing yourself.