Genetic testing for breast cancer

This page was reviewed under our medical and editorial policy by

Eric Fowler, MS, LCGC, Manager, Clinical Genetics, Western Region & Licensed Certified Genetic Counselor

This page was updated on March 8, 2024.

Genetic testing for breast cancer is sometimes used to identify genetic mutations that may increase a patient’s risk of cancer. This may help patients understand their cancer risk. In patients already diagnosed with breast cancer, genetic testing may help patients and doctors make appropriate treatment decisions, while also giving the patient information to pursue risk-reduction strategies and other lifestyle changes.

This guide will help patients and their families learn the basic facts about genetic testing for breast cancer, including:

Is breast cancer genetic?

There’s a genetic link to breast cancer, with about 5 percent to 10 percent of all breast cancer cases known to be hereditary, according to the American Cancer Society (ACS). This means that mutations of specific genes, including the breast cancer gene 1 (BRCA1) and breast cancer gene 2 (BRCA2) changes, may be passed from parent to offspring and increase a person’s lifetime risk for developing breast cancer. Even though the majority of breast cancer cases don’t have a hereditary link, genetic testing is important in helping doctors identify gene mutations that may raise breast cancer risk.

On average, 13 percent of women in the United States will develop breast cancer in their lifetime, according to the National Cancer Institute (NCI). However, for patients with a genetic mutation, this risk increases. In women with the BRCA1 mutation, 55 percent to 72 percent will develop breast cancer at some point; and in women with the BRCA2 mutation, 45 percent to 69 percent will go on to develop breast cancer, according to the NCI.

Genes that may increase breast cancer risk

Several genes have been linked to breast cancer. Some patients may wish to undergo genetic testing to understand their risk of breast cancer, especially if they have a family history of the disease. Undergoing testing is a personal decision. It’s important for patients to talk openly with their doctor about genetic counseling so they may make an informed decision about the pros and cons of testing.

The main benefit of genetic testing is its potential to provide information about cancer risks, allowing patients to make lifestyle changes or decisions, increase the frequency of breast cancer screenings, or take preventive measures to help lower their risk.

Yet, there’s still uncertainty, and genetic testing may have some cons. Knowing whether a patient has a genetic mutation doesn’t necessarily mean he or she will go on to develop cancer. In some patients, knowing about the mutation may lead to increased worry, so some prefer not to know.

Listed below are the genes most commonly associated with breast cancer.

BRCA testing

BRCA1 and BRCA2 are perhaps the two genes most known for their association with breast cancer. Both genes are responsible for repairing damaged DNA through protein production. When mutations (also called pathogenic variants) are inherited, this increases a person’s risk of both breast and ovarian cancers. These mutations, also called germline mutations, may be inherited from either parent.

BRCA1 and BRCA2 testing isn’t recommended for the general population, but it’s recommended for anyone with a family history of cancer, including:

Testing allows patients to find out whether they have a BRCA1 or BRCA2 mutation. If testing shows a positive result for a mutation, they may take steps to reduce their cancer risk by increasing cancer screening or having surgery.

PALB2 mutation testing

Partner and localizer of BRCA2 (PALB2) is a type of genetic mutation closely associated with BRCA2 that causes an increased risk of breast, ovarian and pancreatic cancers. It’s also linked to breast cancer in men. PALB2 mutation is found in about 0.9 percent of breast cancer patients, according to the NCI.

CHEK2 mutation testing

The checkpoint kinase 2 (CHEK2) mutation has been linked to breast cancer and is more frequently found in Eastern and Northern European population groups. CHEK2 genes work to make a tumor suppression protein, but when the gene mutates, this may increase a person’s cancer risk. According to the American Society of Clinical Oncology (ASCO), a CHEK2 gene mutation may increase breast cancer risk 1.5 to three times, with the risk highest in those who have both the CHEK2 mutation and a family history of breast cancer.

TP53 mutation testing

The tumor protein 53 (TP53) gene is involved with tumor suppression, so a TP53 mutation is linked to increased cancer risk. When the TP53 mutation is inherited from a parent, it’s called Li-Fraumeni syndrome (LFS).

Patients with the inherited TP53 mutation have an increased risk of breast and other cancers, with a lifetime risk rate of 90 percent for any type of cancer, according to ASCO. People with TP53 mutations are also more likely to be diagnosed at a younger age.

ATM gene mutation testing

The ataxia-telangiectasia mutated (ATM) gene plays a role in cell growth and division. Research has linked it to an increased risk of breast cancer and poorer treatment outcomes.

Some research studies have found that patients with the ATM gene have about twice the lifetime risk of developing breast cancer, according to ASCO. It’s also linked to an increased risk of other cancers, including prostate, pancreatic and stomach cancers.

CDH1 gene testing

The cadherin 1 (CDH1) gene is responsible for making a protein found in epithelial cells, which cover the surfaces of the body. Genetic mutations in the CDH1 gene are linked to lobular breast cancer—which begins in the milk glands—and may either be inherited or develop in patients who already have lobular breast cancer.

It’s estimated that CDH1 inherited mutations are responsible for a small number of breast cancer cases. CDH1 mutations also increase lifetime risks for a rare type of stomach cancer, called diffuse gastric cancer.

PTEN testing

The phosphatase and tensin homolog (PTEN) gene helps with suppressing tumors, so when it mutates, it may cause an increased risk of both non-cancerous and cancerous tumors. The PTEN mutation is linked to breast, uterine and thyroid cancers. People with PTEN mutations have Cowden syndrome, which is linked with increased risks for cancerous and benign tumors and growths.


Who should consider breast cancer genetic testing?

People considering genetic testing should talk to their doctor to learn more. Genetic testing isn’t recommended for everyone, but research has helped to identify which groups may get the most benefit.

For people who’ve previously been diagnosed with breast cancer, the following people may benefit from testing:

  • Those diagnosed with triple-negative breast cancer 
  • Those diagnosed with metastatic breast cancer
  • Those diagnosed at a younger age
  • Those diagnosed with a second breast cancer
  • Those with a family history of pancreatic, prostate or ovarian cancers
  • Those with a family history of breast cancer, particularly in men or at a younger age
  • Those of Ashkenazi Jewish descent

Other groups of people may also benefit from genetic testing. These include:

  • Those with a family history of a genetic mutation, including BRCA
  • People with a close family history of other cancers, including pancreatic, ovarian and metastatic prostate cancers
  • Women diagnosed with pancreatic or ovarian cancer
  • Men diagnosed with pancreatic, breast or prostate cancer that’s metastatic or high-grade
  • People with a family history of breast cancer, including a relative diagnosed at a younger age, more than one family member diagnosed, or in a male relative

Before breast cancer genetic testing

Before the test begins, a genetic counselor, advanced practitioner or sometimes a physician will perform a risk assessment by taking a three- to four-generation family tree to assess the chances of an inherited risk for cancer and determine whether medical criteria for genetic testing are met. Information about cancer, genetics, potential genetic test results and billing for genetic testing will be provided, and the impact of genetic testing will be considered and discussed. If a decision is made to pursue genetic testing, consent forms will be reviewed and signed.

Genetic testing for breast cancer is performed via a blood test, saliva sample or, less commonly, an oral swab from the cheek. The DNA from the sample will then be tested in a laboratory to look for inherited or germline mutations. No dietary restrictions are required before the testing, and patients are generally allowed to go home immediately afterward. Sometimes, a sample can be collected at home.

Possible genetic test results

After the testing, it may take up to two to three weeks to get results. Patients get their results from their doctor, advanced practitioner or a genetic counselor, a health professional experienced in genetic testing. Genetic counselors play an important role, looking closely at the patient’s family history and discussing specifically what the results mean for the patient.

Possible results from genetic testing range from positive to inconclusive, as detailed below.

Positive: This means an inherited genetic mutation has been found. A positive test result is used to guide cancer screening, may provide opportunities for cancer risk reduction, can help guide treatment for cancer patients, while also providing an opportunity for family members to undergo genetic testing for the familial mutation.

Negative: This means a genetic mutation was not detected. This result significantly reduces the chances for an inherited risk for cancer, but it does not eliminate cancer risks. Personal and family histories still impact cancer risks and should be considered when developing cancer screening plans.

Inconclusive: This means a genetic variant was identified, but it’s not clear how the variant affects the patient’s risk.

Genetic testing may be complex. Genetic counselors are trained to explain in detail what the results mean for each person and are able to answer any questions patients may have about their results.

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