MSI-H and Lynch Syndrome
Microsatellite instability which is caused by deficiency of the DNA MMR system is the molecular abnormality observed in tumors associated with Lynch syndrome. Lynch syndrome represents one of the most frequent conditions of cancer predisposition in human, thus requiring specific care and genetic counseling.
Detection of MSI is important because MSI is the biomarker that identifies cancers more likely to respond to treatment with precision cancer medicines known as PD-1 immune checkpoint inhibitors.
https://news.cancerconnect.com/colon-cancer/understanding-msi-high-and-dna-mismatch-repair