Re-evaluation of human epidermal growth factor receptor 2 (HER2) immunohistochemistry (IHC) 0 or 1+ in metastatic breast cancer (mBC) samples to characterize the proportion of HER2-ultralow (IHC 0 with membrane staining) Read more about Re-evaluation of human epidermal growth factor receptor 2 (HER2) immunohistochemistry (IHC) 0 or 1+ in metastatic breast cancer (mBC) samples to characterize the proportion of HER2-ultralow (IHC 0 with membrane staining)