Mean age at breast cancer diagnosis was significantly lower for CHEK2 c.1100delC carriers than non-carriers (47.9±10.6 years for heterozygous carriers, 41.7±12.6 years for homozygous CHEK2 carriers and 51.2±10.5 years for non-carriers), which is in line with previous studies.48 9 11, 16 28 The median year of breast cancer diagnosis was 2014. Here, CHEK2 is linked to breast cancer.