[15] Heidemann Heidemann S S Double heterozygosity for mutations in BRCA1 and BRCA2 in German breast cancer patients: implications on test strategies and clinical management Double heterozygosity for mutations in BRCA1 and BRCA2 in German breast cancer patients: implications on test strategies and clinical management Breast Cancer Res Treat Breast Cancer Res Treat 2012 2012 134 134 3 3 1229 1229 39 39 22535016 22535016. This evidence concerns the gene BRCA1 and breast cancer.