CHEK2 c.1100delC carriers versus non-carriers had an almost 2.4 fold risk of developing a CBC [HR (95%CI): 2.37 (1.82–3.08), P < 0.001 in all patients and 2.55 (1.87–3.48), P < 0.001 in patients with an ER-positive first primary BC; Table 4] and a 1.3-fold risk of BC death after censoring for CBC occurrence [HR (95%CI): 1.30 (1.09–1.56), P = 0.003 in all patients and 1.38 (1.12–1.71), P = 0.003 in patients with an ER-positive first primary BC; Table 4]. This evidence concerns the gene CHEK2 and complete blood cell count.