Since germinal mutations affecting a single allele in BRCA2 increase susceptibility to BC and OC, while certain bi-allelic mutations cause Fanconi anemia (FA) [49], in similar cases, it is crucial to establish whether the two mutations are in cis or in trans and, therefore, whether are on a same allele or on different alleles. The gene discussed is BRCA2; the disease is Fanconi anemia.