Is Breast Cancer in Your Genes?
What Everyone Should Know about Hereditary Breast Cancer and Genetic Testing
by Ashley Woodson, MS, CGC, and Jennifer Litton, MD
About 1 in 8 women in the U.S. will develop breast cancer over the course of her lifetime. Although, most of the time, the cause may be attributed to a multitude of factors (including age and exposure to estrogen), a small percentage of cases are due to inherited risks. This is called hereditary breast cancer.
What is hereditary breast cancer?
Hereditary breast cancer refers to breast cancers with a specific genetic cause. Approximately 10 percent of all breast cancers are hereditary.
We inherit our genetic information from our parents in the form of genes. Genes are the instruction manuals in our bodies. They are found in every cell and include the coding for things like our eye color and skin color. They can even help protect our bodies from developing cancer.
The most common hereditary breast cancers are linked to two specific genes: BRCA1 and BRCA2. Normally, these genes protect our bodies from developing breast and ovarian cancer. However, if an individual is born with a mistake, or mutation, in one of these genes, that person has an increased chance of developing breast cancer, and developing ovarian cancer, over the course of their lifetime. While the average woman who is diagnosed with breast cancer tends to be diagnosed after age 50, women with inherited forms of breast cancer have a greater risk of having cancer before menopause and may also have an elevated lifetime risk of developing a second breast cancer. Being able to determine whether someone has this hereditary risk can help physicians make decisions about specific cancer screening and preventive measures that can reduce the risk of specific cancers in those people who may be genetically predisposed to them. For example, women with a BRCA1 or BRCA2 gene mutation need increased breast cancer screening, and some opt to undergo prophylactic, risk-reducing surgeries.
Approximately 10 percent of all breast cancers are hereditary.
There are other hereditary factors associated with breast cancer risk beyond the BRCA1 and BRCA2 genes. Researchers have identified several genes linked with elevated risks for breast cancer and are still learning about them. Studies are ongoing to establish the risk of breast cancer, and possibly other cancers, as a result of mutations in these other genes. As this research is ongoing and not complete, this can make it difficult for doctors to recommend specific preventive measures for people who test positive for these genes.
Who should undergo genetic testing?
Many factors play a role in determining which women may be more likely to have a hereditary form of breast cancer. Not all women with breast cancer need to undergo genetic testing. However, you should talk to your healthcare provider about genetic testing if you:
- were diagnosed with breast cancer before age 50
- have a strong family history of breast or ovarian cancer
- are of Ashkenazi Jewish ancestry
- have a specific high-risk pathology, such as triple-negative breast cancer.
Both men and women can inherit genetic factors that may increase their risk for breast cancer, and may choose to undergo genetic breast cancer testing. This may include testing of multiple hereditary factors related to breast cancer risk. Therefore, it’s important to speak with a genetic counselor or another genetics professional to decide what type of testing may be most appropriate. A trained professional can evaluate your family history and assess the likelihood of you having (or being at risk for) hereditary breast cancer.
Talk to your doctor or ask to meet with a genetic counselor if you are concerned about a possible genetic risk of cancer in your family. Knowing your genetic risk for breast cancer can help you (and your family) make treatment decisions and take steps toward prevention.
Ashley Woodson is a senior genetic counselor in the Department of Clinical Cancer Genetics, and 
Dr. Jennifer Litton is an associate professor in the Department of Breast Medical Oncology, at the University of Texas MD Anderson Cancer Center in Houston, TX, where they both work in the High Risk Breast Screening and Genetics Clinic.
This article was published in Coping® with Cancer magazine, November/December 2017.
