ERBB2 and neoplasm: These guidelines identify a tumor as HER2-positive when there is a complete and intense circumferential HER2 IHC staining in ≥10% of cells (score 3+) and/or the gene is amplified with an HER2/CEP17 ratio ≥2.0 and an average HER2 gene (ERBB2) copy number ≥4.0 signals/cell using ISH-based techniques1.