BRCA1 and breast cancer: In total, we identified 48 cases, of whom 18 BC or gynecological cancer patients who did not carry their respective families’ path_BRCA1 or path_BRCA2 variants (n = 13 and n = 5, respectively) came from the Hereditary Cancer Biobank from the Norwegian Radium Hospital, while the Department of Genomic Medicine from the University of Manchester identified a total of 30 BC patients, all non-carriers of the family’s path_BRCA2 variants (Fig. 1).