Positive for Two Copies
of an MYH Mutation

This information is designed for individuals who have been tested for a hereditary cancer syndrome. It will help you understand the results of your test and is best reviewed with your healthcare provider. Please choose the link below that matches your test result by looking at the patient copy of your test result or contacting the healthcare provider who ordered your test.

Overview of FAP and AFAP

Mutations in BOTH copies of the MYH gene cause an adenomatous polyposis syndrome called MYH-associated polyposis (MAP). MAP is associated with the development of multiple adenomas (pre-cancerous polyps) in the colon and rectum, most often more than 10 adenomas over a lifetime. This syndrome also leads to an increased risk of colon/rectal (colorectal) cancer and possibly other types of cancer.

The Genetic Test(s) You Received

  • Comprehensive COLARIS AP®: Full sequence and large rearrangement analysis of the APC gene and a mutation panel of the MYH gene.
  • Gene-Specific COLARIS AP® MYH Analysis: Full sequence analysis of the MYH gene.
  • Gene-Specific COLARIS AP® MYH Mutation Panel: Analysis of the two most common MYH gene mutations in individuals of European ancestry.
  • Single Site COLARIS AP®: Mutation-specific analysis for individuals with known MYH gene mutations in the family.

Your Test Result

  • Positive for Two Copies of an MYH Mutation

Overview of Your Test Result

  • You have mutations or alterations in both copies of your MYH genes.
  • You have an adenomatous polyposis syndrome called MYH-associated polyposis (MAP).
  • Adenomatous polyposis syndromes increase the risk of colorectal adenomas/cancer and, in some cases, other types of cancer.
  • The risk of developing these cancers is less than 100%. Not everyone with an adenomatous polyposis syndrome will develop cancer.

Your Cancer Risks

MYH-associated polyposis is a syndrome that was discovered fairly recently. As a result, information about exact cancer risks is not currently available. Because of the numerous colorectal adenomas that occur in MAP, the colorectal cancer risk is known to be significantly increased. Additionally, it is possible that risks of other cancers, such as stomach and duodenal, may be increased as well. More detailed information about cancer risks in MAP will likely be available in the future. Contact your healthcare provider on a regular basis for up-to-date information on MAP.

Managing Your Risks

Options for reducing cancer risk are available whether or not you have already had a diagnosis of cancer and/or adenomas. Since MAP was discovered fairly recently, there are no specific medical management guidelines for individuals with this particular syndrome. The following are guidelines for two related adenomatous polyposis syndromes, familial adenomatous polyposis (FAP) and attenuated FAP (AFAP). It is recommended that you be managed according to these guidelines, depending on the number of colorectal adenomas (polyps) in you and your family members. Discuss these options with the appropriate medical professionals to determine how you will manage your cancer risks.

Increased Surveillance

Site Procedure Age to Begin Repeat
Colon – FAP
(hundreds to thousands of adenomas)		 Sigmoidoscopy 10-12 years Annually
Colon – AFAP
(between 10 and 99 adenomas over a lifetime) 		Colonoscopy Late teens or early 20s (depending on age of polyp development in the family) 1-3 years
Colon - After colon surgery Endoscopy of remaining rectum and ileal pouch After colon surgery 6 months to 3 years (depending on number of polyps on previous exam)
Duodenum and stomach EGD (examination fo the esophagus, stomach and duodenum) 20-25 years 1-4 years

Surgical Management

  • Preventive removal of the colon and rectum may be recommended depending on the number of polyps.

Chemoprevention

  • Drugs may be used to reduce the number of polyps in any rectum that remains after colon surgery.

It’s a Family Affair

MYH mutations are passed on in a family. Now that these two mutations have been identified in you:

  • Each of your parents is likely a "carrier" of one of your MYH mutations. Your parents can be tested to confirm that this is the case. The risk of colorectal cancer and adenomas in MYH mutation carriers is unclear but it appears that any increase in risk is small and is associated with a later age of onset (usually after age 50).
  • Your biological children will all be MYH mutation carriers. In the rare case that your reproductive partner carries an MYH mutation, your children may inherit two MYH mutations and have MAP. Your partner can be tested to determine if he/she also carries an MYH mutation.
  • Your brothers and sisters have a 25% chance of having the same two MYH mutations identifed in you and a 50% chance of being MYH mutation carriers.
  • More distant relatives (cousins, uncles, and aunts) also may carry one of the MYH mutations identified in you.

Your relatives can be offered Single Site COLARIS AP® to determine whether or not they have the same MYH mutations.

  • Relatives interested in genetic testing will need to know your specific mutations. It is best to provide your relatives with a copy of your test result which you can obtain from your healthcare provider.
  • If your relative is:
    • Positive for two mutations, he/she has the increased cancer risks associated with MAP and can benefit from appropriate medical management.
    • Negative for both mutations, he/she has an average risk of cancer and can follow general population screening guidelines.

If you need a copy of your genetic test result, please contact the healthcare provider who ordered your test.

Next Steps

Please work with your healthcare provider to determine the most appropriate next steps for you.

  • Obtain a copy of your test result.
  • Schedule consultations with appropriate healthcare providers.
  • Create a plan for medical management.
  • Share your genetic test result with your relatives (identify your specific mutation so relatives can have Single Site testing).
  • Re-contact your healthcare provider on a regular basis for new information about MAP.

Additional Resources

Myriad has resources available to help you with your genetic test result.

  • Contact Myriad’s Medical Services Department at 1-800-469-7423 for:
    • Answers to questions about your test result.
    • Information about genetic testing for your relatives.
  • Online tools:

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