About 15% of CRC arise through the MSI pathway and most of these tumors are sporadic.22 However, the IHC study for MMR proteins is recommended for the detection of the hereditary nonpolyposis CRC syndrome (Lynch syndrome) accounting for 1% to 5% of all the cases.23 Moreover, MSI is the only predictive biomarker approved by the FDA for the immune checkpoint blockade inhibitors therapy with pembrolizumab for solid tumors and nivolumab in CRC. This evidence concerns the gene MRC1 and colorectal carcinoma.