CHEK2 and breast cancer: The largest study investigating the prognostic role of CHK2 expression on more than 1000 well characterized breast cancers failed to show a prognostic impact of CHK2 expression in all cancers but revealed associations of high CHK2 expression with poor patient outcome in p53 positive and ER negative cancers while low CHK2 expression was linked to poor prognosis in ER positive cancers [49].