The NCCN Clinical Practice Guidelines in Colon Cancer and Rectal Cancer (2019V1) and 2020 CSCO Guidelines for Colorectal Cancer all recommend that MMR protein and/or MSI testing should be performed in all of the CRC patients, so that a suitable treatment regimen and prognosis evaluation are carried out based on the results of these two methods (6). The gene discussed is MRC1; the disease is colorectal carcinoma.