BRCA1 and breast cancer: Large genome-wide association studies, facilitated by the Consortium of Investigators of Modifiers of BRCA1/BRCA2 (CIMBA2,3), have demonstrated that >60 single nucleotide polymorphisms (SNPs) or small insertions or deletions (Indels) associated with cancer risk in the general population also are associated with breast cancer risk for BRCA1/2 pathogenic variant carriers4–6.