Microsatellite instability (MSI) refers to the condition of genetic hypermutability that results from impaired DNA mismatch repair (MMR). Microsatellites are short, repetitive sequences of DNA, and instability in these regions can lead to significant genetic alterations. In the context of histology, MSI is particularly important in the study of certain cancers, including colorectal, endometrial, and gastric cancers.
