MLH1 and mismatch repair cancer syndrome 1: Of the 285 MMR-deficiency ECs, 169 (59.3%) had combined loss of MLH1 and PMS2, 54 (18.9%) had combined loss of MSH2 and MSH6, 39 (13.7%) had isolated loss of MSH6 and 23 (8.1%) had isolated loss of PMS2 by IHC.