MRC1 and metastatic neoplasm: Although the same patients with intestinal, extraintestinal, primary, and metastatic tumors carry the same MMR germline variations and show no significant differences in the MMR protein-expression levels on IHC staining, different somatic secondary mutation sites and types of the MMR gene, polymorphic variants in the gene structure of tissue cells from different organs, and the immune microenvironment may have an impact on the microsatellite status of these cells, thus occurring in the same Lynch patient.