Among breast tumors in the study, ‘signature 3’ was found to be operative in 255 out of 879 cases, which exceeds the estimated 5% to 10% of breast cancers accounted for by BRCA1/2-mutated tumors [48], supporting the case that ‘signature 3’ captures the effects of HR deficiencies attributable to a variety of means of BRCA1/2 inactivation as well as abnormalities in the function of other genes associated with HR. This evidence concerns the gene BRCA1 and breast cancer.