- MMR IHC Interpretation for the tumor: No loss of nuclear signals of all 4 proteins: Not defective in DNA mismatch repair (non-dMMR or MMRp) and low probability of microsatellite instability-high (MSI-H). Loss of nuclear signals of 1 or more proteins: Defective DNA mismatch repair within the tumor (dMMR). MMR status cannot be determined by IHC.

- MSI status: MSI – stable (MSS) MSI – low (MSI-L) 1% - 29% of the National Cancer Institute (NCI) or mononucleotide markers exhibit instability MSI – low (MSI-L) 1 of the NCI or mononucleotide markers exhibit instability MSI – low (MSI-L) Other (specify): MSI – high (MSI-H) greater or equal 30% of the NCI or mononucleotide markers exhibit instability MSI – high (MSI-H) 2 or more of the NCI or mononucleotide markers exhibit instability MSI – high (MSI-H) Other (specify): MSI - cannot be determined.