Because clinico-pathological features of the tumour are important prognostic factors and BRCA1-associated breast cancers are known to differ in this respect from tumours not associated with BRCA mutations, we paid special attention to a possible role for these factors as confounders or mediators in the association between BRCA1 and BRCA2 mutation carriership and breast cancer survival. This evidence concerns the gene BRCA1 and breast cancer.