In this case, no additional BRCA1 mutations were identified in any of the samples analysed, and the variant allele frequency (VAF) of the original germline BRCA1 4-bp deletion was close to 1 in all tumour samples, consistent with loss-of-heterozygosity (LOH) and maintenance of BRCA1 loss throughout the progression of disease (Fig. 4B). The gene discussed is BRCA1; the disease is neoplasm.