BRCA1 and breast cancer: However, genetic studies involving family-based cancer cases and case-control study groups have consistently shown that potentially pathogenic variants in BARD1 are unlikely to: i) confer a high lifetime risk (OR ≥ 5) to BC and OC in heterozygous carriers akin to pathogenic variants described for BRCA1 and BRCA2; and ii) account for the remaining or a significant proportion of heritability of BC and OC attributable to known cancer predisposing genes, especially in cancer syndromes involving these cancer types.