BRCA1 and breast cancer: We have also analysed available online data from Ambry genetics commercial testing (https://www.ambrygen.com/providers/resources/prevalence-tool, accessed 29/08/2020).23 While it is not possible to assess the level of pretesting for TP53, and BRCA1/2 or the presence of a Li Fraumeni family history, there is a clear upward trend of prevalence of BRCA1 and BRCA2 PVs with reducing age at breast cancer until 26 years of age (online supplemental table 3).