<prompt> Immunohistochemical markers are used in various cancers. Her-2Neu immunohistochemistry in breast cancer is used for:Diagnosing purposePredicting response to therapyScreening of Ca breastRecurrence of Ca breast  <response>: HER2, also known as neu or c-erbB-2, is a member of the epidermal growth factor receptor EGFR family and is one of the best-characterized tyrosine kinases. The HER2 gene is frequently amplified and the protein is overexpressed in many cancers, including breast, ovarian, lung, gastric, and oral cancers. HER2 overexpression is associated with increased cell proliferation and anchorage-independent growth as well as resistance to proapoptotic stimuli. HER-2neu amplification overexpression markers in breast cancer have been validated to predict response to therapy in breast cancer. Ref: Meric-Bernstam F., Pollock R.E. 2010. Chapter 10. Oncology. In F.C. Brunicardi, D.K. Andersen, T.R. Billiar, D.L. Dunn, J.G. Hunter, J.B. Matthews, R.E. Pollock Eds, Schwazs Principles of Surgery, 9e. 