Identification of this subset of HER2+ breast cancers is essential to avoid overtreatment of patients with small HER2+, ER+ breast cancers, who may be optimally treated with endocrine therapy alone, or in combination with a HER2-directed agent, thereby avoiding the use of chemotherapy.9 In our study, 75 patients are IHC/FISH HER2+/HR+ of whom 36 (48 %) are BluePrint Luminal with a significantly lower pCR rate (3 %) to NCT/trastuzumab versus the 33 IHC/FISH HER2+/HR+ patients (44 %) who are BluePrint HER2 (pCR = 45 %). Here, ERBB2 is linked to breast cancer.