T1N0 BC patients diagnosed between 2009 and 2017 were included and classified into three subgroups according to receptor status: 1) hormonal receptor (HR)+/human epidermal growth factor receptor-2 (HER2)−; 2) HER2+; and 3) triple negative (TN) (HR−/HER2−). Here, ERBB2 is linked to breast cancer.