Abstract
To determine the genetic components that constitute polygenic traits in familial or sporadic breast cancer, low-risk variants on the one hand and mutations conferring moderate penetrance on the other hand have to be identified. While members of the latter group were found by comprehensive screening of candidate genes which are, like the 2 highly penetrant genes BRCA1/BRCA2, located in the DNA repair pathway, the development of novel techniques was urgently needed to identify low-risk variants. The hybridization of chips which contain several hundred thousand single nucleotide polymorphisms (SNPs) with several thousand DNAs from either sporadic breast cancer cases or healthy controls (genome-wide association study, GWAS) has already led to the detection of at least 8 low-risk variants, conferring odds ratios of 1.06-1.64. As they are common in the population, it is likely that extended GWAS will develop a genetic pattern that is able to discriminate women suitable or not for population screening programs.