Immunohistochemistry screening (IHC)

IHC screening looks to see if certain proteins are absent in the tumor sample, indicating that one of the Lynch syndrome genes might not be working properly. Lynch syndrome mutations affect whether the MLHL, MSH2, MSH6, and PMS2 proteins are made and located in the correct place.

 Test Results, their meaning and the next Steps
Test Result What it means Next Step
Absent MLH1 and PMS2 proteins Test could not determine if you are likely to have Lynch syndrome Further testing needed
Absent MSH2 and MSH6 proteins You are likely to have Lynch syndrome Genetic counseling and testing
Absent MSH6 protein You are likely to have Lynch syndrome Genetic counseling and testing
Absent PSM2 protein You are likely to have Lynch syndrome Genetic counseling and testing
All 4 proteins present You are unlikely to have Lynch syndrome No additional testing is needed, unless you have a strong family history of colorectal cancer, or had colorectal cancer before age 50