Absence of linkage to the ataxia telangiectasia locus in familial breast cancer.

Heterozygotes for ataxia-telangiectasia (AT) are known to have an increased risk of breast cancer. The gene (or genes) responsible for almost all cases of AT has been localised to chromosome 11q by genetic linkage analysis. To examine the possibility that AT heterozygosity may account for a substantial proportion of familial breast cancer, we have typed five markers on chromosome 11q in 16 breast cancer families. We have found no evidence for linkage between breast cancer and chromosome 11q markers and conclude that the contribution of AT to familial breast cancer is likely to be minimal.