ERBB2 and metastatic neoplasm: A low percentage of HR + phenotype in HER2 IHC-0 and HER2 IHC-3 tumors, while a higher frequency of HR + phenotype in HER2 IHC-1 and IHC-2/no amplification tumors than tumors with other HER2 expression levels in both primary and metastatic tumors (Fig. 1A).