HBOC is caused by pathogenic variants in BRCA1/2 which confer substantially elevated risks for female breast cancer, ovarian cancer, and male breast cancer (in particular for BRCA2 carriers), in addition to increased risks for pancreatic cancer, prostate cancer, and melanoma (The Breast Cancer Linkage Consortium, 1999; Brose et al., 2002; Levine et al., 2003; Lindor et al., 2008; Lynch et al., 2009; Moran et al., 2012; Mavaddat et al., 2013; McKay et al., 2016). This evidence concerns the gene BRCA1 and breast cancer.