ERBB2 and breast cancer: Small node-negative, hormone receptor (HR)–positive, ERBB2 (previously HER2/neu)–positive tumors represent a heterogenous category of breast cancer, with recurrence rates ranging from less than 5% up to 25% at 5 years, with or without adjuvant treatments.1,2 The current National Comprehensive Cancer Network guideline3 acknowledges the lack of representation of T1a and T1b tumors in prior randomized trials and, thus, recommends the consideration of chemotherapy for tumors 1 cm or smaller at the discretion of clinicians.