The 21-gene recurrence score (RS) assay has been widely used to assess the risk of disease recurrence among early-stage invasive breast cancer patients.9–12 Both the American Society of Clinical Oncology (ASCO) and National Comprehensive Cancer Network (NCCN) guidelines have recommended the 21-gene RS in the management of oestrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative early-stage invasive breast cancer patients. Here, ERBB2 is linked to invasive breast carcinoma.