This is particularly interesting if we consider that HER2 has always been accounted as a factor of endocrine resistance in BC, with the capability of attenuating the effects of endocrine therapy [22], and suggests that hormonal metabolic pathway is still active in HER2-positive tumors and plays a role in determining the behavior of disease, even in presence of adequate HER2 blockade. This evidence concerns the gene ERBB2 and breast cancer.