Monoallelic inactivating germline mutations in PALB2 were subsequently shown to be associated with familial breast cancer [3] and numerous studies supported this association in various populations and established a mutation prevalence of approximately 1 % among familial breast cancer cases (varying from 0.1 % to 2.7 % as reviewed by Southey et al. [4]). This evidence concerns the gene PALB2 and breast cancer.