BRCA1 and breast cancer: In addition, in a related project studying the effect of BRCA1, BRCA2 and CHEK2*1100delC germline mutations on survival and disease outcome in a large cohort of unselected breast cancer patients (diagnosis before 50 years of age), we found that the tumour characteristics of CHEK2*1100delC carriers did not differ significantly from those of non-carriers.