Examples of prognostic biomarkers are Prostate-Specific Antigen (PSA) in prostate cancer and the phosphatidylinositol 3-kinase (PIK3CA) mutation status of tumours - which are associated with human epidermal growth factor receptor 2 (HER2) in women with positive metastatic breast cancer6. The gene discussed is ERBB2; the disease is prostate carcinoma.