CHEK2 and complete blood cell count: For known BRCA1/2 mutation carriers, studies have shown a 30–40 % risk of CBC at 10 years, and the risk appears to continue beyond 10 years.13 The CBC risk for carriers of other genes such as CHEK2, p53, PALB2, ATM, and NBN is less well studied, and at this time there is insufficient evidence to support an increased CBC risk for these mutations.