Evaluation of endometrial tumours for MMR deficiency can identify patients with Lynch syndrome, an autosomal dominant mutation in the DNA of MMR proteins (MLH1, MSH2, MSH6 or PMS2 and EPCAM). Approximately 1 in 279 to 1 in 400 individuals is affected by Lynch syndrome and 3% of endometrial cancers are attributable to Lynch syndrome [8, 9]. The gene discussed is PMS2; the disease is Lynch syndrome.