ERBB2 and breast carcinoma: HER2-positive (+) breast cancers represent ~ 15% of all breast cancers.1 Early data suggested that women diagnosed with HER2+ early breast cancer faced an elevated risk of recurrence and experienced poorer survival outcomes compared with those with HER2-negative disease.2 For many years chemotherapy with anthracyclines and taxanes was standard of care for all patients with HER2+ breast cancer.