Further analysis of dMMR patients for tumor MMR gene defects identified 23 cases (18.70%) with MSH2 defects, 83 cases (67.48%) with MLH1 defects, 27 cases (21.95%) with MSH6 defects, and 94 cases (76.42%) with PMS2 defects. The gene discussed is MSH2; the disease is neoplasm.