It is estimated that 0.5% to 1% of the general population are HetAT, and studies conducted in hereditary breast and ovarian cancer (HBOC) families or early-onset BC cases showed that deleterious ATM alleles confer a two- to four-fold increase in BC risk for carriers as compared with non-carriers [9, 10]. The gene discussed is ATM; the disease is Hereditary breast and ovarian cancer syndrome.