ERBB2 and metastatic neoplasm: Peter C Thuss-Patience et al. provided some explanations for this result: First, for some reasons, such as discordant HER2 expression between the primary tumor and the metastatic tumor (Peng et al., 2015) or varying HER2 expression after first-line chemotherapy with or without trastuzumab in metastatic disease (Ishimine et al., 2015), the molecular profile of the tumor was altered.