Breast Cancer Genetics

Breast cancer risk is influenced by both genetics and environmental factors. Being aware of your degree of genetic risk can help with early detection of the disease, which is the best way to achieve a good breast cancer prognosis and enjoy a long and healthy life.

Breast Cancer Risk: Family History

Even without being tested for specific breast cancer genes, you can get a good sense of your genetic predisposition by looking at your family. You have an increased risk of developing the disease if you have a first-degree relative, such as a mother, sister or daughter, who has had it. The more first-degree relatives that have had the disease, the higher your personal risk.

The occurrence of ovarian cancer in the family is another warning sign that you may be more likely to develop breast cancer. Discuss your family history with your physician if any of your ancestors or members of your immediate family have had breast or ovarian cancer.

Breast Cancer Genes

Scientists are learning more about the genetics of breast cancer every day. A number of genes have been associated with a higher risk of breast cancer.

The most well-publicized breast cancer gene, and the one associated with the highest risk of developing the disease, is BRCA1. Another gene–BRCA2–causes significantly increased risk, as well. All people have these genes; only when you inherit certain mutated forms does your breast cancer risk increase.

According to the American Cancer Society (2009), approximately 5 to 10 percent of all breast cancer cases are caused by BRCA gene mutations. Women who inherit the mutated version of BRCA1 or BRCA2 have a 57 or 49 percent chance, respectively, of developing breast cancer by age 70. Fortunately, less than 1 percent of the population carries the harmful versions of these breast cancer genes.

Genetic Research for Breast Cancer

Though BRCA1 and BRCA2 are the main genes responsible for increasing the risk of breast cancer, variants of other genes have been shown to increase the risk as well, including CDH1, PTEN1, STK11 and TP53.

Furthermore, there are a few genes that some studies have shown to increase the risk, but other studies have not. These genes are suspected, but not confirmed, to increase the risk of breast cancer:

  • AR
  • ATM
  • BARD1
  • BRIP1
  • CHEK2
  • NBN
  • PALB2
  • RAD50
  • RAD51.

Other Genetic Risk Factors

People with certain genetic syndromes–such as Li-Fraumeni Syndrome or Cowden Syndrome–may have an increased risk of developing breast cancer. African-American and Caucasian heritages seem to increase the risk as well.

For these, and for all genetic risk factors, remember that risk is inherited, not the disease itself. Having a genetic predisposition doesn’t guarantee that you’ll develop the disease, only that you’re at a higher risk of doing so.

What Can You do with This Knowledge?

An understanding of the genetics of breast cancer is a crucial aspect of breast cancer awareness. If you suspect that your family history puts you at risk, consult your physician. She may recommend genetic testing to determine if you have one of the breast cancer genes.

Regardless of the outcome of such testing, and even in the absence of a family history, be vigilant for the signs of breast cancer. Speak to your doctor about how to perform monthly breast cancer self-exams.


The American Cancer Society. (2009). Breast cancer facts and figures 2009-2010. Retrieved on October 11, 2010 from

Genetics Home Reference. (2007). Breast cancer. Retrieved October 12, 2010 from