ERBB2 and breast carcinoma: Although hormone receptor (HR) status has been established as a predictor of pCR in patients with HER2-positive breast cancer who are treated with neoadjuvant HER2-blockade, it does not accurately differentiate between non-responders and responders, as both patients with HR-negative disease and patients with HR-positive disease benefit from pertuzumab [1–3, 5].