Fifteen of the 16 somatic genetic events leading to bi-allelic inactivation of the PALB2 wild-type allele were predicted to be clonal (Fig. 1, Supplementary Table 3), suggesting that bi-allelic PALB2 inactivation and subsequent complete loss-of-function of PALB2 may constitute an early somatic event in the development of a subset of PALB2-associated breast cancers. This evidence concerns the gene PALB2 and breast cancer.