ERBB2 and neoplasm: This redefined the spectrum of HER2 expression from a binary (positive or negative) to a spectrum including HER2-low (IHC 1+ or 2+ , in-situ-hybridization (ISH) negative) and HER2-ultralow (faint, incomplete membrane staining in \documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\ge$$\end{document}≥ 10% of tumor cells, less than IHC 1+) [124–126].