Genetic testing

Lynch syndrome genetic and predictive testing

We can carry out genetic tests to investigate whether Lynch syndrome runs in your family.

Blood tests

We can take blood tests to check the Lynch-related genes for mutations. 

Tumour tests

There are also 2 different tests we can do on a stored tumour sample (biopsy) that can tell us if Lynch syndrome is likely.

Immunohistochemistry (IHC) staining test

This test looks at the proteins that are made by Lynch-related genes. If any of the proteins are not found in the tumour, this suggests that the gene that makes that protein is not working properly. This could be due to an inherited mutation in that gene.

If all the proteins are detected in the tumour, Lynch syndrome is very unlikely.

Promoter hypermethylation test

This test is used when the MLH1 protein is not found in the IHC test. This test looks to see if the MLH1 gene is responsible for the missing protein(s) by testing if this gene was turned off in the tumour only. If the gene is turned off only in the tumour, then Lynch syndrome is very unlikely.

If the gene is turned off in the tumour and in the normal tissue and blood, then this could be due to an inherited mutation in that gene, and Lynch syndrome is possible. 

We may offer each of these tumour tests first to clarify whether genetic testing is going to be helpful for a family, and to clarify which Lynch-related gene to test.

There can sometimes be difficulties in getting the tumour sample which may delay or prevent testing.

If tumour testing shows that Lynch syndrome is likely, further genetic testing would ideally require a blood sample from someone in your family who has had bowel cancer or another Lynch syndrome-related cancer. If we identify a gene mutation in an affected relative, further testing may be available to other relatives who are at risk.

Resource number 4200/VER3
Published date March 2023
Review date March 2026

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