Some women with a family history of breast cancer have genetic mutations that raise their risk. And while genes are just one risk factor for the disease, knowing your status can help you make some important decisions.
Women with mutations in the genes BRCA1 or BRCA2 are five times more likely to be diagnosed with breast cancer, according to the National Cancer Institute. That means that 60 percent of women with a BRCA mutation will develop breast cancer in their lifetime, compared to 12 percent of women in the general population.
But less than 1 percent of women actually have a BRCA mutation, making costly genetic testing unnecessary for most. While the decision to get tested is a personal one, here are some guidelines that can help you make the call:
For women who are not of Ashkenazi Jewish descent, the NCI recommends genetic testing if you have:
Two first-degree relatives diagnosed with breast cancer, with one of them before age 51. First-degree relatives include your mother or sister;
Three or more first- or second-degree relatives diagnosed with breast cancer. Second-degree relatives include your grandmother or aunt;
A combination of first- and second-degree relatives diagnosed with breast cancer or ovarian cancer;
A first-degree relative diagnosed with cancer in both breasts;
A combination of first- or second-degree relatives diagnosed with ovarian cancer;
A first- or second-degree relative diagnosed with breast and ovarian cancer;
A male relative diagnosed with breast cancer.
For women of Ashkenazi Jewish descent, who are more likely to carry a specific BRCA2 mutation passed from generation to generation, the NCI recommends genetic testing if you have:
A first-degree relative diagnosed with breast or ovarian cancer;
Two second-degree relatives on the same side of the family diagnosed with breast or ovarian cancer.
About 2 percent of adult women have a family history pattern described above but, again, less than 1 percent of women will have a BRCA mutation.
"Not every woman in such families carries a harmful BRCA1 or BRCA2 mutation, and not every cancer in such families is linked to a harmful mutation in one of these genes," according to the NCI website. "Furthermore, not every woman who has a harmful BRCA1 or BRCA2 mutation will develop breast and/or ovarian cancer."
Women without one of the family history patterns described above are unlikely to have a harmful BRCA mutation, according to the NCI.
Carrying a BRCA gene mutation does not guarantee a breast cancer diagnosis, but some women opt to reduce their risk with surgery. In May, Angelina Jolie explained her decision to surgically remove both breasts -- an operation known as a preventive double mastectomy -- after testing positive for a BRCA1 gene mutation.
"Once I knew that this was my reality, I decided to be proactive and to minimize the risk as much as I could," wrote the 38-year-old actress, who lost her mother to ovarian cancer in 2007 and her aunt to breast cancer in 2013.
Studies suggest that preventive mastectomy can reduce breast cancer risk by about 90 percent in high-risk women, according to the NCI. But surgery carries risks, too, so women are advised to talk to their doctors about the procedure's pros, cons and possible alternatives.
Click here for more information from the National Cancer Institute.