Approximately 2-4% of endometrial cancer (10% in women diagnosed under the age of 50) is attributable to Lynch syndrome,1,2,3,4 an autosomal dominant cancer-prone syndrome caused by germline mutations in the MLH1, MSH2, MSH6 or PMS2 genes, which encode components of the DNA mismatch repair (MMR) pathway, or, in a small proportion of cases, by deletions in the EPCAM gene that lead to epigenetic silencing of the adjacent MSH2 gene (reviewed in 5). The gene discussed is MLH1; the disease is endometrial cancer.