Lynch Syndrome

Who should undergo genetic testing for Lynch syndrome?

Occasionally, tumour or cancer testing may reveal results that can help guide if Lynch syndrome testing is needed for you. These tumour tests include:

1. Immunohistochemistry (IHC) testing for MMR proteins
   • IHC testing can determine which MMR proteins are present or absent within the tumour
   • The absence or loss of any MMR proteins is suggestive of Lynch syndrome and genetic testing may be offered to you
     
2. Microsatellite instability (MSI) testing
   • Microsatellites are regions of repeated DNA that show instability if the MMR proteins do not function properly
   • MSI testing evaluates for the presence of functional MMR proteins
   • Tumours that are MSI-high (i.e., high microsatellite instability) are suggestive of Lynch syndrome and genetic testing may be offered to you
   
   

You may be recommended to undergo additional tests to determine if genetic testing is needed for you.

Your personal and/or family history of cancer can also help guide if genetic testing for Lynch syndrome is needed. If you or your family members meet one or more of the following criteria, you can consider genetic testing:

• Colorectal/uterine cancer diagnosed at or under the age of 50
• Colorectal/uterine cancer diagnosed with loss of MMR proteins on IHC tumour testing
• Colorectal/uterine cancer diagnosed with MSI-high result on tumour tissue
• Combination of colorectal/uterine cancer and another Lynch syndrome-related cancer*
• Two or more family members on the same side of the family diagnosed with any Lynch syndrome-related cancer*, with one diagnosed at or under the age of 50
• Three or more family members on the same side of the family diagnosed with any Lynch syndrome-related cancer* at any age
• A previously identified faulty MMR gene in the family

*Lynch syndrome-related cancers:

• Colorectal
• Uterine (endometrial)
• Ovarian
• Gastric
• Renal pelvis and/or ureter
• Bladder
• Biliary tract
• Pancreatic
• Brain/central nervous system
• Prostate
• Breast

Note: This list may change as more information is available

How can your genetic test result help you?

1. Personalised management
   Your genetic test result may help to personalise your management options based on your cancer risk.

    

   If you have a cancer diagnosis

   • Can help guide important treatment and sometimes surgical decisions
   • Indicates what other cancers you are at risk of and how to manage these risks

    
   

   If you are currently cancer-free

   • Can help guide relevant screening to detect cancer at its earliest, most treatable stage
   • Can help guide decisions regarding relevant cancer riskreducing procedures like surgery (not standard management)
   • Can help carriers consider dedicated reproductive options when family planning

    
   

2. Familial implications
   Your genetic test result can also help you understand if other family members are at risk of Lynch syndrome. They can subsequently consider their own testing (predictive testing) to clarify their carrier status to determine tumour and cancer risks.
   
   Family members who have inherited the same faulty MMR gene may be at increased risk of tumours and cancer and can benefit from management options such as screening (to detect tumours and cancer at an early and manageable stage) or surgery (to reduce their risk of cancer).
   
   Family members who did not inherit the faulty MMR gene can avoid unnecessary screening and worry. Their children will also not be at risk.