BRCA1- and BRCA2-deficient breast cancers from WSI had 0.60 and 0.41 median proportion of signature 3 compared to median of 0 in BRCA-proficient breast cancers (P = 2.2 x 10−28 and 1.9 x 10−16, respectively; Fig 1A). Here, BRCA1 is linked to breast cancer.