High-ranking Catalogue of Somatic Mutations in Cancer (COSMIC) Breast Cancer gene (BRCA) point mutational signature cosegregates with a high prevalence of structural variants, termed the unstable genomic subtype, and deleterious mutations in HR repair pathway genes such as BRCA1 and 2 and PALB24 (Figure 1B and Supplementary Tables 8-10). Here, BRCA1 is linked to breast cancer.