CHEK2 and breast cancer: The prevalence of the CHEK2*1100delC variant among women with and without breast cancer varies among countries (Meijers-Heijboer et al, 2002; Vahteristo et al, 2002; Osorio et al, 2004; Huzarski et al, 2005; Kilpivaara et al, 2005; Bernstein et al, 2006; Weischer et al, 2007).