VENTANA Pathway anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody (VENTANA HER2 (4B5)) is intended for the semi-quantitative detection of HER2 antigen in sections of formalin-fixed, paraffin-embedded normal and neoplastic breast and gastric tissue on a VENTANA automated IHC/ISH slide staining device. It is indicated as an aid in the assessment of breast and gastric cancer patients for whom Herceptin treatment is considered and for breast cancer patients for whom Kadcyla (trastuzumab emtansine) or Perjeta (pertuzumab) treatments are being considered.