From a set of previously whole-genome sequenced (WGS) tumours20, we selected 22 Luminal A or Luminal B subtype tumours classified as either ‘aromatase-inhibitor-sensitive' (N=12, median surgical Ki67=1.1%, range 0–7.0%) or ‘aromatase-inhibitor-resistant' (N=10, median surgical Ki67 24.6%, range 10.4–47.1%). This evidence concerns the gene CYP19A1 and neoplasm.