ERBB2 and breast carcinoma: The specific combination of receptor status has a significant impact on the outcome of these targeted therapies; HER2/neu-positive breast cancer is less responsive to any type of endocrine treatment [29]; approximately one-half of HER2/neu-positive breast cancers are also ER-positive, and this breast cancer subgroup (luminal B) is thus more refractory to endocrine therapy – despite the ER-positive status.