CHEK2 and breast cancer: To understand better the association of CHEK2 variants and breast cancer risk in the general population in the USA, we analyzed the frequency of three CHEK2 variants – 1100delC, R145W, and I175T, each of which reportedly alters CHEK2 protein function – in a population based, case–control study of 506 breast cancer cases diagnosed before age 45 years from western Washington state, and a set of 459 frequency matched control individuals.