MLH1 and Leigh syndrome: For example, Kaneko (42) suggested that dMMR ECs with MLH1- PHM had a worse prognosis than pMMR ECs and Lynch syndrome (LS) associated dMMR ECs (dMMR ECs without MLH1-PHM); Sloan (43) found that the expression of PD-L1 was the highest in LS-associated dMMR ECs, followed by dMMR ECs with MLH1-PHM and finally pMMR ECs.