Classification of samples by breast cancer intrinsic subtypes revealed 86.7% concordance for tumor–PDX pairs, where 26 (70.3%) of PDXs were basal-like, 10 (27.0%) were HER2-enriched (HER2E) and one (2.7%) was luminal B (Fig. 3a). The gene discussed is ERBB2; the disease is breast carcinoma.