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Genetic risk factors: Recent studies have shown that about 5% to 10% of breast cancer cases are hereditary as a result of gene changes (mutations). The most common gene changes are those of the BRCA1 and BRCA2 genes. Normally, these genes help to prevent cancer by making proteins that keep cells from growing abnormally. However, if you have inherited either mutated gene from a parent, you are at increased risk for breast cancer.
See the section "Do We Know What Causes Breast Cancer?" for more information about genes and DNA. Women with an inherited BRCA1 or BRCA2 mutation have up to an 80% chance of developing breast cancer during their lifetime and at a younger age than those women who are not born with one of these gene mutations in their cells. Women with these inherited mutations also have an increased risk for developing ovarian cancer.
Other genes have been discovered that might also lead to inherited breast cancers. One of these is the ATM gene. ATM stands for ataxia-telangiectasia mutation. The gene is responsible for repairing damaged DNA. Certain families with a high rate of breast cancer have been found to have mutations of this gene. Another gene, the CHEK-2 gene, also increases breast cancer risk when it is mutated. Neither one of these genes, however, is a frequent cause of familial breast cancer.
Inherited mutations of the p53 tumor suppressor gene can also increase your risk of developing breast cancer, as well as leukemia, brain tumors, and/or sarcomas (cancer of bones or connective tissue). The Li-Fraumeni syndrome, named after the 2 researchers who described this inherited cancer syndrome, is a rare cause of breast cancer.
If you are considering genetic testing, it is strongly recommended that first you talk to a genetic counselor, nurse, or doctor qualified to interpret and explain these tests, before being tested. It is very important to understand and carefully weigh the benefits and risks of genetic testing before these tests are done. Testing is expensive and is not covered by some health plans. There is concern that people with abnormal genetic test results will not be able to get life insurance or that coverage may only be available at a much higher cost, but many states have passed laws that prevent insurance companies from denying insurance on the basis of genetic testing. To learn about your state, you can go to this internet site --
http://www.ncsl.org/programs/health/genetics/ndishlth.htm
For more information, see our position statement on genetic testing or go to the National Cancer Institute site on genetic testing for breast cancer.
Family history of breast cancer: Breast cancer risk is higher among women whose close blood relatives have this disease. Your risk of developing breast cancer is increased if:
You have 2 or more relatives with breast or ovarian cancer.
Breast cancer occurs before age 50 in a relative (mother, sister, grandmother or aunt) on either side of the family. The risk is higher if your mother or sister has a history of breast cancer.
You have relatives with both breast and ovarian cancer.
You have 1 or more relatives with two cancers (breast and ovarian, or 2 different breast cancers).
You have a male relative (or relatives) with breast cancer.
You have a family history of breast or ovarian cancer and Ashkenazi Jewish heritage.
Your family history includes a history of diseases associated with hereditary breast cancer such as Li-Fraumeni or Cowdens Syndromes.
Having 1 first-degree relative (mother, sister, or daughter) with breast cancer approximately doubles a woman's risk, and having 2 first-degree relatives increases her risk 5-fold. Although the exact risk is not known, women with a family history of breast cancer in a father or brother also have an increased risk of breast cancer. Altogether, about 20% to 30% of women with breast cancer have a family member with this disease.
