A microsatellite is a tandem repeat sequence of the human genome, generally between 1 and 6 bp, and is also called short tandem repeats (STRs) or simple sequence repeats (SSRs).

Microsatellite Instability (MSI) refers to the reduction or increase in the number of repetitions of microsatellites. The inherent mechanism of microsatellite instability is the mismatch repair (MMR) system maladjustment, which limits the body that can correct the spontaneous length changes of microsatellites. The ability of cells to mutate, somatic mutations accumulate, and eventually form MSI.

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