This signature 3 is strongly associated with mutations in BRCA1 or BRCA2, genomic deletion and insertion events smaller than 100 kb, and a deficiency in homologous recombination repair in breast cancer.31 In the absence of substantial numbers of indels and genomic deletion and insertion events in our WGS data, additional support for recombination repair deficiency is lacking. Here, BRCA1 is linked to breast cancer.