Inherited and acquired defects in homologous recombination, a phenotype termed 'BRCAness', may lend to therapeutic exploitation in breast cancer. To this end, development and clinical evaluation of platforms to identify signatures of BRCAness are of immense interest. In this issue of Breast Cancer Research, Vollebergh and colleagues report that a BRCA-like array comparative genomic hybridization (aCGH) genomic instability signature is associated with benefit from high-dose cyclophosphamide-thiotepa-carboplatin chemotherapy. We discuss the strengths and weaknesses of this study and consider the clinical significance and applicability of this aCGH BRCAness signature in the context of other existing homologous recombination deficiency detection platforms.