BRCA1 and breast cancer: Furthermore, in the BEACCON study (“hereditary BrEAst Case CONtrol study”) (Li et al., 2021), which was conducted to investigate the monogenic causes underlying the familial aggregation of BC beyond BRCA1 and BRCA2, the prevalence of rare missense variants in CHEK2 was 2.11% (122 cases) versus 1.24% (71 control cases), with an OR 1.73 (CI: 1.27–2.35).