No increased susceptibility to breast cancer from combined CHEK2 1100delC genotype and the HLA class III region risk factors

The 1100delC mutation and the HLA risk haplotype confer increased breast cancer risks, but an interactive effect on breast cancer between both factors is unlikely. In contrast, the effect of 1100delC mutation on breast cancer risk was limited to individuals without HLA risk haplotype, suggesting a mutual excluding effect between these risk factors.