At variance with BRCA1- and BRCA2-associated BCs, but akin to ATM-associated BCs, only one (20%) of the TCGA high-risk–variant CHEK2-associated BCs displayed a high LST score (Figure 2C) and none of the five CHEK2-associated breast cancers subjected to WES harbored a dominant mutational signature 3 (Figure 2D;, Supplementary Figure 7, available online), consistent with the results of Polak et al. (16) and Riaz et al. (14). Here, ATM is linked to breast cancer.