Half of the 10 mutation carriers (5 of 83; 6% of the entire cohort) were found to harbor PVs in widely accepted BC susceptibility genes (i.e., PALB2, ATM, and CHEK2), whereas the remaining half (5 of 83; 6% of the entire cohort) carried PVs in candidate genes for which no firm association with BC incidence has yet been established in a heterozygous germline setting (CDKN2A, RUNX1, FANCI, WRN, and RECQL4). This evidence concerns the gene RECQL4 and breast cancer.