Neoadjuvant chemotherapy (NAC) is the gold standard of care for breast cancer and increases the options for breast-conserving surgery.1–3 Pathological complete response (pCR) after NAC is currently acknowledged as an indicator of good outcome, especially in triple-negative breast cancer (TNBC) and human epidermal growth factor receptor 2 (HER2)-enriched breast cancer (HER2BC).4 One previous study indicated that residual cancer cells after NAC may be more aggressive or have enhanced metastatic potential.5 However, some patients who fail to achieve pCR after NAC have a relatively good outcome. The gene discussed is ERBB2; the disease is breast cancer.