Notably, MSI assessment by IHC has only indirect significance since the loss of function of the Lynch syndrome genes does not always lead to the development of MSI in the tumor, and there is also a possibility of false-positive IHC results, occurring in 5–11% of cases due to non-functional MMR proteins with a preserved antibody-binding capacity, the dislocation of functional MMR proteins in cells, focal losses, and other reasons [1,11]. This evidence concerns the gene MRC1 and neoplasm.