This compares favourably with preceding series where the conversion to constitutional testing was poor and pathogenic variants were assumed from allele frequency in adjacent normal tissue.18–21 Third, we tested 15 women with strong clinical risk factors whose ovarian tumours were MMR proficient, facilitating an assessment of the accuracy of MMR IHC as a prescreen for LS constitutional testing, which is poorly reported in the literature. This evidence concerns the gene MRC1 and ovarian neoplasm.