MSH2 and neoplasm: Other advantages of MSI analysis over IHC include the possibility of identifying a tumor that has defective MMR but retained staining on IHC (i.e., due to non-truncating missense mutation) or one that has defective MMR as a result of mutations in other genes besides hMLH1, hMSH2, or hMSH6 and thus would be missed by IHC [33].