Indeed, for BRCA1 and BRCA2, monoallelic LOF variants present in the germline can result in a nearly tenfold increased lifetime risk of developing breast cancer (Antoniou et al., 2003, 2014), whereas bi-allelic LOF variants cause Fanconi anemia (FA) (Howlett et al., 2002; Sawyer et al., 2015). This evidence concerns the gene BRCA1 and breast cancer.