OncotypeDx (Genomic Health, Redwood City, CA, USA), a 21-gene breast cancer recurrence score (RS) assay, has both prognostic and predictive value for estrogen receptor positive (ER+)/human epidermal growth factor receptor 2 negative (HER2−)/lymph node negative breast cancer patients1,2. The gene discussed is ERBB2; the disease is breast carcinoma.