MRC1 and neoplasm: Clarke and Cooper state an overall sensitivity of 96-100% for the four MMR protein markers in an MMR-IHC proficiency test “using tissue microarrays of carcinomas of known germline MMR mutation status”.14 The rest of their paper relates to endometrial cancer, but the authors do not specify whether the proficiency testing results (which are described as unpublished) relate to endometrial tumours, or colorectal tumours, or both, or whether the tumours were from unselected cases or cases ascertained through family cancer clinics.