MSH6 and Lynch syndrome: Alternatively, dMMR is observed in patients with Lynch syndrome, caused by autosomal dominant heterozygous germline variants in MLH1, MSH2, PMS2, MSH6, or a large deletion encompassing one or more exons of EPCAM and the promoter region of MSH2. These patients have an increased risk for colorectal, endometrial, gastric, pancreatic, brain, biliary tract, urinary tract and ovarian tumors1,3.