MLH1 and neoplasm: If the MLH1 protein is deleted in surgical specimens, it is necessary to continue the detection of B-raf (B-Raf proto-oncogene, BRAF) oncogene and promoter methylation of MLH1 gene in tumor tissues, this is because about 75% of patients with MLH1 protein deletion are not LS patients and the loss of MLH1 protein in surgical specimens is usually caused by promoter methylation of MLH1 gene.