Signs of an Inherited Mutation

What are the signs of a cancer gene mutation?

It's important to know your family medical history and share your personal medical history with your relatives. Here are some common signs that indicate there could be an inherited mutation causing cancer in a family.

You have a blood relative who tested positive for an inherited mutation.

Ask your relatives to share the results of any genetic testing they have had. It helps to know which test was done, which genes were tested, whether any mutations were found, and how the results were explained by a genetics expert.

You or a close relative has been diagnosed with any of these cancers at any age: 

• pancreatic cancer
• ovarian, fallopian tube or primary peritoneal cancer
• male breast cancer
• triple-negative breast cancer
• cancer in both breasts or two separate cancers in the same breast
• prostate cancer that is metastatic, very-high or high-risk based on pathology, or intermediate-risk with a pathology result called intraductal/cribriform histology
• a type of rare stomach cancer known as diffuse gastric cancer
• 3 or more melanomas
• other rare types of cancer 

You or a close relative has been diagnosed with the following cancers at a younger-than-average age: 

• breast cancer at age 50 or younger
• colorectal cancer at age 50 or younger
• endometrial cancer at age 50 or younger
• gastric cancer at age 50 or younger
• prostate cancer at age 55 or younger
• childhood cancer

Multiple people on the same side of your family were diagnosed with any combination of the following: 

• breast, ovarian, pancreatic, prostate cancer or melanoma
• colorectal, endometrial, gastric, ovarian, pancreatic, urothelial, brain, biliary tract, small intestine or certain types of skin cancer

You are Ashkenazi Jewish and you or a close relative has been diagnosed with any of the following cancers:

• breast
• ovarian, fallopian tube or primary peritoneal cancer
• pancreatic
• prostate

As you review your family history, it's important to keep in mind the following:

• These signs can suggest an inherited mutation, but many families with one or more of these signs will not have a mutation.
• Even in families where a mutation is found, some relatives will test negative.
• This is not a complete list of all the possible signs of an inherited mutation. 

A genetics expert can help you understand whether the cancer in your family may be hereditary and whether genetic testing could be helpful.

Genetic testing for people diagnosed with cancer

Expert guidelines outline situations where people diagnosed with cancer may benefit from genetic testing. These are summarized below. 

Genetic testing for surgical or treatment decisions

Genetic test results can sometimes affect cancer treatment or surgical decisions. Testing may help people and their healthcare team choose treatments that are more likely to work and avoid options that may be less effective or unnecessary.

Ask your doctor if genetic testing might affect your treatment or surgical choices. This may include people who have:

• Early‑stage breast cancer who are deciding between lumpectomy and mastectomy, including whether to consider risk‑reducing surgery.
• High‑risk, HER2‑negative early‑stage breast cancer, where a germline mutation (such as BRCA1 or BRCA2) may affect eligibility for treatment with a PARP inhibitor.
• Metastatic HER2‑negative breast cancer, where certain inherited mutations may guide treatment options, including PARP inhibitors.
• Ovarian cancer, especially stage 3 or 4 disease, where inherited mutations may affect treatment and maintenance therapy options.
• Metastatic prostate cancer, where inherited mutations may affect treatment choices, including targeted therapies.
• Advanced pancreatic cancer, where inherited mutations may affect treatment options or eligibility for targeted therapies.
• Colorectal cancer, where inherited cancer syndromes (such as Lynch syndrome) may affect surgical planning and follow‑up care.
• Endometrial (uterine) cancer, where testing for inherited cancer syndromes may affect treatment, screening for other cancers, and family risk.
• Advanced, recurrent, or hard‑to‑treat cancers, especially when standard treatment options are limited and genetic test results could guide therapy or clinical trial options.
• Cancer diagnosed at a younger‑than‑expected age, or cancer along with a personal or family history that raises concern for an inherited mutation.

Additional guidelines for genetic testing in people with a cancer diagnosis

For people diagnosed with cancer, additional guidelines outline who may benefit from genetic testing. You can read more about genetic testing for each of the following cancer types:

• breast cancer
• colorectal cancer
• endometrial cancer
• melanoma
• ovarian, fallopian tube or primary peritoneal cancer
• pancreatic cancer
• prostate cancer

A genetics expert can help determine whether genetic testing may be useful for guiding treatment decisions and what type of testing is appropriate.

Other situations where genetic counseling and testing may be beneficial

The guidelines recommend speakiing with a genetics expert if any of the following situations applies: 

• you have had colon polyps with the following features found on pathology:
  • 10 or more adenomatous polyps.
  • 2 or more hamartomatous polyps.
  • 5 or more serrated polyps.
  • 5 or more polyps close to the rectum. 
• pathology of the fallopian tubes after surgery found a type of precancerous change known as a serous tubal intraepithelial carcinoma (STIC) lesion.

Repeating genetic testing for people who had testing in the past

Genetic testing has improved over the years and labs are able to find mutations that were previously missed through older testing methods. If you had genetic testing in the past, you may benefit from additional genetic counseling and testing in the following situations:

• You had limited genetic testing in the past with a test that only looked for one or a few genes and your results were negative.
• You had genetic testing before 2014 and your results were negative.
• There have been new cancers diagnosed in the family that are not explained by earlier genetic test results, even if you or another family member previously tested positive for a mutation. In these cases, updated genetic counseling and testing may help determine whether another inherited mutation could be involved.