To compare allelic variation in type and location of pathogenic variants across the BRCA1 protein between the early age at onset and the control cohort, we compared the pathogenic variant accumulation in different regions of BRCA1. Whereas no differences were detected for the Breast Cancer Cluster Regions (BCCRs), which are associated with increased risk of breast cancer (Additional file 4: Figure S1a), differences were found for the Ovarian Cancer Cluster Region (OCCR). This evidence concerns the gene BRCA1 and breast cancer.