MRC1 and Familial prostate cancer: Furthermore, the authors describe prostate tumours as the only BRCA2-mutated prostate cancers with a similar rate of biallelic loss (70%) in cases with germline and somatic alterations.22 A lower ratio of germline:somatic alterations have been reported for components of the MMR pathway in prostate cancer, as less than a quarter (22%) of the tumours identified by Abida et al.21 as MMR deficient harboured a germline mutation.