Neoadjuvant chemotherapy (NACT) offers an increased rate of breast conserving surgery, can downsize advanced breast tumours to allow surgery and with the addition of human epidermal growth factor receptor 2 (HER2)-targeted therapy (to NACT or adjuvant chemotherapy) can improve survival in HER2-positive breast cancer.1 However, NACT comes at the cost of significant side-effects and it is therefore important to identify non-responders to NACT as early as possible. The gene discussed is ERBB2; the disease is breast cancer.