A retrospective cohort study of 3333 women with stage I–II (cT1–T2) HER2+ breast cancer treated with upfront surgery without neoadjuvant therapy in 2018 demonstrated that tumour size was the strongest predictor of nodal positivity—both T1c and T2 disease were associated with increased nodal positivity with pathology [17]. The gene discussed is ERBB2; the disease is breast carcinoma.