In Finland, recurrent mutations explain most of the familial breast cancer risk caused by the currently known susceptibility genes, such as BRCA1, BRCA2, PALB2, and CHEK2 (Sarantaus et al. 2000; Erkko et al. 2007; Vahteristo et al. 2002), whereas in other more diverse populations several rare mutations in each gene have been identified. Here, BRCA1 is linked to breast cancer.