Microsatellite Instability (MSI) and Mismatch Repair Protein Analysis
Expression of the MMR proteins involved, MSH2, MLH1, MSH6 and PMS2 can be detected by immunohistochemistry. No or low expression of one or more of these is indicative of MSI and should be further tested as below.
Five markers have been recommended by the National Cancer Institute to screen for MSI in HNPCC tumors (often called Bethesda markers). Generally, MSI detection in >30% of the markers is considered to be MSI-high (MSI-H) whereas microsatellite abnormalities in <30% of the markers is considered MSI-low.
Correlation between MMR protein expression and MSI is essential for patient management.
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Last updated: 07/08/2015