When should I refer a patient for genetic counseling regarding Lynch Syndrome?

Refer a patient for genetic counseling regarding Lynch syndrome if they have a personal or family history suggestive of mismatch repair (MMR) gene pathogenic variants, which increase susceptibility to colorectal, endometrial, ovarian, and other related cancers.

Specifically, referral should be considered when there is:

• A diagnosis of colorectal or endometrial cancer at a young age (typically under 50 years).
• A strong family history of Lynch syndrome-associated cancers, including colorectal, endometrial, ovarian, gastric, small bowel, urinary tract, or brain cancers, especially if multiple relatives across generations are affected.
• Evidence of MMR deficiency in tumor testing (e.g., immunohistochemistry or microsatellite instability testing) indicating possible Lynch syndrome.
• Known pathogenic variant in a mismatch repair gene in the family.

Referral to specialist genetics services is recommended for formal genetic counseling, risk assessment, and consideration of genetic testing to confirm Lynch syndrome and guide management.

This approach aligns with UK guidelines emphasizing the identification of individuals with pathogenic variants in mismatch repair genes and the importance of genetic counseling and testing in families with strong histories of related cancers ¹.