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Genetic testing for altered breast cancer genes

Learn all about genetic testing for breast cancer, which is used to find out whether an altered gene, such as BRCA1 or BRCA2, runs in the family.

1. What is genetic testing for breast cancer?

Some people have a higher risk of developing breast cancer because they have inherited an altered gene.

Genetic testing is used to find out whether an altered runs in the family.

An altered gene may also be referred to as a gene change, fault, variant or mutation.

2. BRCA1, BRCA2, PALB2 and other altered genes

The most common inherited altered genes that increase the risk of breast cancer are called BRCA1 and BRCA2 (BRCA stands for BReast CAncer). 

BRCA1 and BRCA2 genes usually protect us from developing breast and ovarian cancer. However, inheriting an alteration in 1 of these genes increases the risk of developing cancer.

Other less common altered genes may also increase the risk.

How common are altered genes?

Around 5% to 10% of women with breast cancer are thought to carry an altered gene.  

Do altered genes only affect women? 

Both women and men can inherit, carry and pass on an altered gene that increases the risk of breast cancer. 

While a man with an altered gene is less likely to develop breast cancer himself, he can pass the altered gene on to his children.

When thinking about family history of breast cancer, it’s important to consider relatives on both the mother’s and father’s side of the family.

3. Who can have genetic testing?

You may be eligible for genetic testing if:

  1. You've been assessed as having a significant family history of breast or ovarian cancer
  2. An inherited altered gene has already been identified in your family 
  3. Your own diagnosis of breast cancer means you’re eligible for genetic testing

Genetic testing is available in the NHS usually through genetics centres for people who have had genetic counselling. 

At some hospitals pre-test counselling and genetic testing may be offered by the breast and gynaecology treatment teams.  

Your genetics or specialist team will tell you if genetic testing is an option for you. 

If you’re concerned about your family history speak to your GP or treatment team. 

4. Deciding whether to have genetic testing

If genetic testing is an option for you, it’s your decision whether to have the test. 

Deciding whether to have genetic testing is a difficult and complex process, and some people who are eligible may decide not to have the test. 

Advantages of having genetic testing

If you’re found to carry an altered gene, you can take steps to manage your cancer risk. For example, you might have regular screening or risk-reducing treatment.

It may also mean family members can make choices about having their own risk assessed and managing their risk.

Disadvantages of having genetic testing 

For some women, the thought of finding out they have an altered gene may lead to increased anxiety.

Depending on your age, not all risk-management options might be available if you’re found to carry an altered gene. 

Helping you decide

If you’re having difficulty deciding, your genetics team can support you in making your decision.  

There’s no right or wrong answer. It’s important you have all the information you need to make a decision you feel comfortable with.   

Talking to someone who has had a similar experience can be helpful. Through our Someone Like Me service, you can speak to someone who has had genetic testing - please see further below.

You may also find it helpful to talk to our nurses by calling our helpline, the details for which are at the top and bottom of this page.

If you decide not to have genetic testing, your genetics team will talk to you about managing your risk. Depending on your situation you may still be offered regular screening to check for breast cancer. 

5. The testing process

There are two stages to genetic testing.

Stage 1: a full screen (diagnostic testing)

The first stage involves testing a relative who has had cancer to try to find out if a known altered gene runs in the family.  

This will usually be a relative who has had breast or ovarian cancer, but in some cases it might be a relative who has had prostate cancer. 

Altered genes can be difficult to find. There’s a better chance of finding an altered gene in someone who has already been diagnosed with breast or ovarian cancer. 

A blood sample is taken and sent to a laboratory to be tested for known altered genes.  

If you have had breast or ovarian cancer, you can have the test yourself. 

In rare circumstances, if no relatives are available for testing and you have not had cancer, you may be able to have the test yourself. Your genetics team will tell you if this is an option.

The results

Results are usually available within 1 to 3 months. Your genetics team will let you know how the results will be given to you. You may have a clinic appointment, a telephone call or have the results sent in the post. 

There are 3 possible outcomes:

A positive result

If an altered gene is found (a positive result), this confirms your chances of developing breast cancer are higher than the general population.  

Your genetics team will know which gene runs in your family. They can then search for the alteration more easily in other family members, who can be tested to see if they also carry it (predictive genetic testing).

A negative result

A negative result means a known altered gene was not found.  

If an altered gene has not been identified, other family members will not be offered genetic testing.  

However, if you have a strong family history your risk of developing breast cancer may still be higher than the general population. Your genetics team can discuss your individual risk and options for managing your risk.  

A variant of unknown significance (VUS)

In a small number of cases, a variant of unknown or uncertain significance (VUS) may be found. This means an alteration was found in a known breast cancer gene, but it’s not yet known if this particular alteration increases the risk of developing breast cancer. 

Your genetics team will tell you and family members how to interpret the results of this first test.

Stage 2: a predictive genetic test (targeted genetic test)

If an altered gene is found in one family member during the full screen, other blood relatives can be tested to see whether they also carry the identified altered gene. 

The results

The results of a predictive genetic test usually take around 4 to 8 weeks.

Whatever the results of your test, it’s important that you can talk through any questions or concerns about your results with your genetics team. 

If you do not have an altered gene

If the predictive genetic test shows you do not have the altered gene that was found in your family (a negative result), your risk of developing breast cancer is the same as women in the general population.

This also means any children you have, or may have in the future, will not inherit this altered gene. 

If you have an altered gene

If the test shows you have inherited the altered gene found in your family (a positive result), your chance of developing breast cancer, and possibly other cancers, is much higher than the general population. 

This does not mean you will definitely develop breast cancer. 

Your genetics team will discuss what options are available for you to manage your risk. 

The options offered to you may include:

  1. Regular screening
  2. Drug treatment 
  3. Risk-reducing surgery

You can read more about these options in our booklet Family history of breast cancer: managing your risk.

However, you do not have to take up any of these options if you choose not to.  

You’re likely to have many questions such as how to tell your family and whether to have screening or risk-reducing treatment. Your genetics team will support you during this time.

Getting the results of your genetic test can be a difficult and uncertain time.  You’ll be offered post-test counselling and your genetics team will be able to support you and talk through your feelings and concerns. 

6. Direct-to-consumer genetic testing kits

In recent years genetic home testing kits that can be ordered online and completed at home have become widely available.  

Although these home testing kits look at an individual’s genetic information, what they are testing for and the level of detail may vary between tests.  

Home testing kits may give you inaccurate information about your level of risk of developing particular genetic disorders. 

If you have concerns about your family history you should always speak to your GP.  

Genetic Cancer Alliance has more information on direct-to-consumer genetic testing.

7. Cancer risks for gene carriers

A person with an altered gene is sometimes referred to as a gene carrier. 

Being a gene carrier does not mean you will develop breast cancer, ovarian cancer or related cancers. 

However, you do have a higher risk than the general population.  

General population

During their lifetime, women have a:

  • 15% risk of breast cancer 
  • 2% risk of ovarian cancer

BRCA1 

Women with an altered BRCA1 gene have a:

  • 60% to 90% risk of breast cancer
  • 40% to 60% risk of ovarian cancer

Men with an altered BRCA1 gene have a 0.1% to 1% risk of breast cancer.

BRCA2 

Women with an altered BRCA2 gene have a:

  • 45% to 85% risk of breast cancer
  • 10% to 30% risk of ovarian cancer 

Men with an altered BRCA2 gene have a 5% to 10% risk of breast cancer, and up to 25% risk of prostate cancer. 

Less common altered genes

PALB2 

Women with an altered PALB2 gene have a 44% to 63% risk of breast cancer.

TP53 

Women with an altered have an up to 85% risk of breast cancer.

The lifetime risk for a person with an altered TP53 gene to develop any type of cancer is 90%.

CHEK2

Women with an altered CHEK2 gene have a moderate risk of developing breast cancer.

Moderate risk is higher than the general population. But it’s still more likely they will not get breast cancer.

ATM 

Women with an altered ATM gene have a moderate risk of developing breast cancer.

Moderate risk is higher than the general population. However, it’s still more likely they will not get breast cancer. 

Other genes 

Some genetic conditions caused by rare altered genes are also associated with breast cancer.

These include:

  • Peutz-Jegher syndrome (altered STK11 gene)
  • Cowden syndrome/PTEN hamartoma tumour syndrome (altered PTEN gene)
  • Hereditary diffuse gastric (stomach) cancer syndrome (altered E-cadherin (CDH1) gene)
  • Neurofibromatosis type 1 (altered NF1 gene)

If one of these runs in your family, your genetics team will talk to you about your risk of breast cancer.

Information for gene carriers 

If you have been told you carry an altered gene, you may find it useful to read our booklet Family history of breast cancer: managing your risk.

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Quality assurance

Last reviewed in January 2022. The next planned review begins in January 2024.

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