CHEK2 and breast cancer: CHEK2 was the gene that carried the highest number of pathogenic variants after BRCA1 and BRCA2. We observed no evidence of an association between pathogenic variants in this gene and breast cancer risk in our main analyses (OR 1.3 [95% CI: 0.53–3, p = 0.6]), though there was evidence of an association from unadjusted analyses (p = 0.0009; Supplementary Table 4), which give biased estimates of risk but valid tests of association.