MSI Cancer Immunotherapy Screening - Microsatellite Instability (MSI) Test

The immunohistochemical assay for microsatellite instability (MSI) or loss of mismatch repair (MMR) protein expression aims to evaluate the status of four key proteins in the MMR system (MLH1, MSH2, MSH6, and PMS2) within cancer cell nuclei. It determines whether a tumor exhibits high microsatellite instability (MSI-H), which is associated with loss of expression of one or more of these proteins, thus making it a candidate for immunotherapy.