CHEK2 and breast cancer: Previous research has shown an association between the 1100delC deletion and risk of breast cancer in women, with the estimated risk being approximately twofold.6 7 A similar association has been seen for other PTVs in aggregate.6 8 Rare CHEK2 missense variants (MSVs), in aggregate, have also been associated with breast cancer risk, with a relative risk (RR) of ~1.4.6