MRC1 and cancer: The MSI analysis has many benefits: it is appropriate for FFPE tissue samples, it does not require experienced pathologist, it can detect MSI cancers that have non-functional MMR system but retained MMR proteins expression on IHC due to non-truncated missense mutation, it can recognize MMR abnormality due to mutations of MMR proteins that are not listed in the IHC panel [25], and it is comparatively less exposed to alteration than IHC following the administration of radiation and neoadjuvant therapy.