MSI (Microsatellite Instability)

Microsatellite instability (MSI) refers to changes or mutations in small repetitive sequences of DNA called microsatellites. These changes often occur when the DNA repair systems fail to correct errors that arise during cell division. MSI is significant in cancer, particularly colorectal and endometrial cancers, as it can indicate a specific type known as mismatch repair deficiency. Detecting MSI helps guide treatment options, as tumors with high MSI may respond better to certain immunotherapies. In summary, MSI is a marker of genetic instability linked to the development and behavior of some cancers.