Breast Cancer Genetic Testing

February 13, 2026

This page was reviewed under our medical and editorial policy by Heather Hampel, M.S., C.G.C., professor, and Susan Yost, Ph.D., staff scientist, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte

While some lifestyle habits — such as smoking and excessive alcohol consumption — or harmful exposures to chemicals or radiation may increase a person’s risk for developing cancer, inherited gene mutations may also be a risk factor. A mutation is a harmful change in the cell’s genetic blueprint or instructions (known as DNA). These changes may increase the risk for developing cancer.

For this reason, people with a family history of cancer or other high risk factors may be interested in genetic testing for breast cancer. The testing results may give patients more information to guide preventive steps, screening and treatment decisions.

What Is Genetic Testing for Breast Cancer?

To run a genetic test for breast cancer, a blood, saliva, or cheek cell sample is sent to a lab. A lab analyzes the sample and returns the results. The test may look for mutations in multiple genes associated with breast and sometimes other cancers.

Genetic testing for breast cancer may let a person know if his or her cancer risk or a family history of cancer is caused by an inherited gene mutation. For people who have had cancer in the past, testing may help them learn about their risk for developing another cancer in the future. Other factors, such as Ashkenazi Jewish heritage, may also be tied to breast cancer risk and mutations.

With the exception of triple-negative breast cancer, if only one person in a family has been diagnosed with breast cancer after age 60 without other close family members who have had breast, ovarian, pancreatic or prostate cancer, it's less likely to be hereditary. If a person has an inherited gene mutation, it means his or her risk for developing cancer is increased. It does not mean that he or she will definitely get cancer.

Genetic counselors help people decide if they should have genetic testing by explaining the possible risks, benefits and limitations of testing and what the results mean. Insurance companies may require that certain criteria are met before covering the cost of the tests.

How Accurate Is Genetic Testing for Breast Cancer?

Genetic testing performed by a regulated lab is generally very accurate. Genetic testing for breast cancer should be handled by a lab regulated by the Clinical Laboratory Improvement Amendments (CLIA) program. This program ensures that federal standards for accuracy, quality and reliability are met. Direct-to-consumer genetic tests are not required to meet CLIA standards. 

When test results come in, it's important for each patient to meet with a genetic counselor to discuss what they mean. Genetic testing is an evolving field, with experts continually learning more in order to refine test panels for breast cancer. Results are based on what is known today. 

For instance, a patient may receive results that are negative for any mutations in the breast cancer genes that are known today. However, more breast cancer genes may be discovered in the future for which they may not have had testing so patients with a strong family history may need to repeat their testing in five to 10 years. In addition, some genetic changes may be difficult to interpret or even considered harmless now, but additional research may lead to them being reclassified as cancer-causing mutations in the future as more is learned. A genetic counselor helps patients interpret the results and answer questions, which may ease anxiety related to test results.

Is Breast Cancer Genetic?

All cancers are caused by mutations in genes that cause the cells to grow too quickly and not die when they should. However, most of the time, those mutations are acquired during a person's lifetime and not inherited. According to the American Cancer Society, roughly 5% to 10% of breast cancer cases are due to inherited genetic mutations. While there are other known risk factors, why a person develops breast cancer is often unclear.

Mutations in the BRCA1 and BRCA2 genes are among those most often associated with increased breast cancer risk, but they also increase a person’s risk for developing cancers of the ovaries, prostate, pancreas and skin.

Mutations in other genes, such as ATM, CDH1, CHEK2, PALB2, PTEN and TP53, are also associated with breast cancer. Researchers are learning more about other genes that may affect breast cancer risk, and new ones may emerge over time.

Types of Breast Cancer Genetic Tests

In most cases, a multi-gene panel test will be ordered. This type of test checks several genes at the same time and may be useful when a family has no known gene mutations. Some of the genes that are typically included in multi-gene panel tests for breast cancer are listed below.

ATM Gene Testing

The ataxia-telangiectasia mutated (ATM) gene is linked to a condition known as ataxis telangiectasia (AT). People with AT may have poor muscle coordination, dilated blood vessels in the eyes and certain immune problems. People with a mutation in their ATM gene do not have AT, they are just carriers for that autosomal recessive condition. However, it has been found that ATM carriers have an increased risk for developing breast, ovarian, prostate, and pancreatic cancers. 

BRCA Gene Testing

There are two types of BRCA or breast cancer genes, BRCA1 and BRCA2. These genes help repair damaged DNA, so a mutation means damaged DNA does not get fixed. This may lead to cancer. People with a mutation in one or both of these genes have an increased risk for developing breast, ovarian, prostate, pancreatic and skin cancers, as well as some other types of cancer. More than 60% of women who inherit a BRCA1 or BRCA2 mutation will get breast cancer at some point in their lifetime, according to the National Cancer Institute.

CDH1 Gene Testing

CDH1, also known as the cadherin 1 gene, provides genetic instructions for the production of a protein called epithelial cadherin (E-cadherin). This protein is found in the covering of cells in various areas of the body. E-cadherin not only causes cells to group together and form tissues, but it also prevents uncontrolled cell growth. People with a CDH1 gene mutation have an increased risk for developing invasive cancer in milk-producing cells of the breast (lobular breast cancer) and a type of gastric cancer that is more difficult to detect because it spreads throughout the wall of the stomach instead of making a visible mass on the lining of the stomach (diffuse gastric cancer).

CHEK2 Gene Testing

Checkpoint kinase 2 (CHEK2) is a tumor suppressor gene involved in DNA repair as well as the regulation of cell growth when DNA damage occurs. Mutations in this gene are linked to an increased risk of breast cancer. The increased risk for developing breast cancer in people with a CHEK2 mutation ranges from 20% to 44%, depending on whether or not other immediate family members are affected, according to researchers in the journal Breast Cancer.

PALB2 Testing

The PALB2 gene — short for partner and localizer of BRCA2 — works with BRCA2 to repair damaged DNA. Women with a PALB2 mutation may be 35% more likely to develop cancer by their 70th birthday than those without the mutation, according to Yale School of Medicine. Individuals with a CHEK2 mutation also have an increased risk for ovarian, pancreatic and prostate cancers.

PTEN Gene Testing

PTEN is a tumor suppressor gene, which means it prevents the uncontrolled growth of cells. The acronym stands for phosphatase and tensin homolog deleted on chromosome 10. People with mutations in this gene are at higher risk for developing cancers of the breast, thyroid, colon, endometrium or kidneys.

TP53 Testing

The BRCA genes’ role in breast cancer is better known, but TP53 is the most frequently mutated gene in breast cancer. Short for transcription factor p53, the TP53 gene is mutated in about 30% of all breast cancers, according to researchers in Trends in Cancer. TP53 is involved with cell growth, death and DNA repair. Inherited mutations in the TP53 gene cause a rare hereditary cancer syndrome called Li Fraumeni syndrome, with increased risks for many cancers including breast, sarcoma, leukemia, lung and adrenal cancer.

How Long Does Genetic Testing Take?

Genetic testing for breast cancer is typically performed using a saliva or blood sample, so the test itself takes very little time. In most cases, results are available within two to three weeks.

Breast Cancer Genetic Test Results

The results of genetic testing for breast cancer are typically listed as positive, negative, inconclusive or uncertain.

Positive result: This means a mutation (harmful gene change) linked to an increased risk of cancer was found. For a person diagnosed with breast cancer, this information may help guide treatment decisions. For someone without cancer, this result may help them decide if they should:

• Have additional screenings or checks
• Have preventive surgery or start medications to reduce their cancer risk
• Make certain lifestyle changes, such as quitting smoking, eating healthier or exercising
• Seek advice about fertility and pregnancy
• Share test results with other family members who may wish to know their own risk

Negative result: The lab found no harmful genetic changes that might increase cancer risk. This result is especially helpful in families with a known genetic mutation because it means the person tested did not inherit it. This result is known as a true negative. It means the person’s cancer risk is about the same as that of the general population. When a person has a strong family history of cancer but has no associated gene mutation, the negative result is known as an uninformative negative. This means a genetic mutation may be still involved, but it was not detected by our current technology. Doctors may recommend further testing or checkups as new technology becomes available.

Inconclusive result: A genetic change was found, but there is not yet enough information to know whether it increases cancer risk. This type of genetic change is referred to as a variant of uncertain significance (VUS). People with this finding are urged to stay in touch with their provider in case new information becomes available about their variant over time.

At City of Hope, care team members use the results of genetic testing to provide personalized and comprehensive care.