Hereditary Cancer and Genetic Testing

Understanding genetic test results

Genetic testing for an inherited mutation can have three possible results:


Positive for a mutation

A positive genetic test result means that an inherited mutation was found in a gene (or sometimes in more than one gene) that is associated with increased cancer risk. Genetic testing companies and healthcare professionals may use different terms for an inherited mutation, such as “pathogenic variant” or “deleterious mutation” on a test result report. 

If you test positive for an inherited mutation, your lifetime risk for cancer may be increased compared to someone who does not have an inherited mutation. Your risk for cancer will depend on several factors, including:

  • which gene has the mutation
  • your gender
  • your age
  • your personal and family medical history

A positive genetic test means that other relatives may have also inherited the same mutation. 

For a list of genes, their associated cancer risks, related guidelines and medical options, visit this section of our website.


Negative for a mutation

A negative genetic test result means that no mutation was found in any of the genes that were included in the test panel. A negative genetic test can have several meanings, depending on the personal and family medical history of the person tested.

  • In a family where a genetic mutation has already been identified, a negative test may be considered a "true negative." This means that the person tested does not have a higher risk for cancer than the general population. 
  • In some families with multiple cases of cancer, genetic testing does not reveal any answers. In a family with many cases of cancer where all members test negative for a mutation, this type of result is called  "uninformative negative." The term "uninformative" means that experts cannot find the cause of the cancer in the family. Families with uninformative negative results are encouraged to contact a genetics expert regularly to update their medical history and learn if any new genetic tests might provide additional information. 


Additional testing for people who previously tested 

Genetic testing has improved, and laboratories can now find gene mutations that may have previously been missed. Genetic tests ordered before 2014 were more limited than current tests. Members of families with old uninformative test results may want to consider repeat testing. 

specialist in cancer genetics is the best person to interpret genetic test results and to help you decide whether additional genetic test may be right for you or your family. 


Variant of uncertain significance (VUS)

A VUS result means that a change was found that may or may not increase the risk for cancer. Not all changes in genes are harmful. Some changes may be harmless, while others can cause the body to make proteins that don’t work correctly.

A VUS result means that at the time of testing, the lab cannot tell whether the gene change is harmful and increases the risk for cancer or harmless and doesn't increase cancer risk. Less-studied genes included on newer gene panels are more likely to return a VUS result. As more people have panel testing and more research is done, labs will be better able to tell whether a VUS is harmful or harmless. Visit our Research Search and Enroll Tool to find research studies enrolling people with a VUS

For people with a VUS result, experts base cancer screening, prevention and treatment recommendations on their personal and family medical history. People who receive a VUS result should speak with a genetics expert to understand their risks and medical options and to learn if their variant has been reclassified as harmful.

key-facts
  • FORCE recommends that people see a genetics expert before and after genetic testing in order to assure the proper test is ordered and results are explained correctly. 
  • Genetic testing does not always lead to an answer about cancer risk. 
  • Some people may benefit from repeat testing with new technology, especially those who had genetic testing before 2014. 
  • Experts rely on personal and family medical history to make recommendations for people with a VUS result. 
  • People who received cancer genetic testing as part of DNA testing for ancestry should speak with a genetics expert about confirming their results. 
clinical-trials
  • NCT02665195: Prospective Registry Of MultiPlex Testing (PROMPT). PROMPT is an online research registry. The goal of PROMPT is to help researchers to better understand the risks that are linked to mutations and VUS in less well-studied genes. People who have had multi-gene panel testing with either a positive test result or a VUS result can enroll in PROMPT to help researchers learn more about cancer risks. 
Last updated July 20, 2020