Whereas all MMR-deficient endometrioid cancers were MSI and showed loss of MLH1/PMS2 proteins in five of 32 cases, MSH2/MSH6 in two of 32 cases, and isolated MSH6 in one of 32 cases; the MMR-deficient serous carcinoma was microsatellite stable and showed PMS2 protein loss and an altered pattern of MLH1 with putative partial MLH1 protein loss [121]. The gene discussed is MSH6; the disease is serous adenocarcinoma.