Notably, PALB2 bi-allelic inactivation is present in a large proportion of PALB2-associated breast cancers, and the mechanisms leading to this include both LOH of the wild-type allele or pathogenic somatic mutations affecting PALB2. Importantly, the 12 PALB2-associated breast cancers with PALB2 bi-allelic inactivation displayed genomic features consistent with HRD, and shared similarities in terms of genetic instability and genomic features of HRD with BRCA1-associated and BRCA2-associated breast cancers with bi-allelic inactivation. The gene discussed is BRCA1; the disease is breast cancer.