PMS2 and neoplasm: The MMRd/microsatellite unstable molecular subtype accounts for 25–30% of all ECs and they have an intermediate prognosis.9, , , , –14 These tumours have loss of DNA mismatch repair, which results in a high mutational burden (‘hypermutated’), exceeding >10 mutations per megabase.9 Mismatch repair deficiency can be identified through microsatellite instability testing, or testing for the loss of expression of one or more mismatch repair proteins (MLH1, PMS2, MSH6, PMS2).