Microsatellite Instability

Microsatellite instability (MSI) is a condition where the DNA repair system in cells fails to fix small errors that occur during DNA copying, especially in repetitive DNA sequences called microsatellites. Normally, these errors are corrected, but when repair mechanisms are defective, the errors pile up, leading to genetic instability. MSI is associated with some cancers, notably certain colorectal and endometrial cancers, indicating a failure in the body's ability to correct DNA mistakes, which can contribute to the development and progression of tumors. Testing for MSI helps guide diagnosis and treatment options.