CHEK2 and breast cancer: Truncating CHEK2 founder mutations (c.1100delC, IVS2 + 1G > A, del5395) confer a higher than twofold increase in the risk of breast cancer [1–3], whereas p.I157T (c.470 T > C, rs17879961), a CHEK2 missense mutation is associated with a milder, 1.4-fold elevation in the risk [4].