In contrast, case-control mutation screening of CHEK2 revealed an approximately equal contribution from T + SJVs and rMSs to the fraction of breast cancer attributable to rare variants in that gene, and a case-control mutation screening meta-analysis of ATM revealed that rMS in that gene may actually be responsible for a larger fraction of the breast cancer attributable to rare variants than are the T + SJVs [19,20]. This evidence concerns the gene CHEK2 and breast cancer.