Biomarkers
HER2 Amplification
Also known as: HER2-positive, HER2+, ERBB2 amplification
Definition
Overexpression or gene amplification of HER2 protein, targetable with specific therapies in breast, gastric, and other cancers.
Detailed Explanation
HER2 testing is done by IHC (scored 0, 1+, 2+, 3+) and/or FISH for gene amplification. HER2-positive cancers (IHC 3+ or FISH-amplified) are treated with trastuzumab (Herceptin), pertuzumab, T-DM1, or Enhertu. HER2-low (IHC 1+ or 2+ without amplification) is now targetable with Enhertu. Testing is standard in breast and gastric cancer.