Indeed, considering that this patient was treated with anti-estrogen therapy in the adjuvant setting, and that this same ERBB2 activating mutation has been reported to arise in patients treated with anti-estrogen therapy [33], our results support a model in which the ERBB2 V777L mutation was acquired and selected for after primary tumor dissemination in response to endocrine therapy administered following primary tumor resection. This evidence concerns the gene ERBB2 and neoplasm.