Test Details: Immunohistochemical testing helps to identify specific antigens (proteins) within tissue sections utilizing an antigen-specific antibody. Estrogen receptor (ER) and Progesterone receptor (PR) expression is seen in tumours of female sex steroid hormone responsive tissues such as the breast, endometrium, and ovary. It predicts response to hormonal therapy and is a prognostic marker for survival in breast cancer patients. Over-expression of HER-2/neu is associated with poor prognosis of breast, ovarian, bladder, pancreatic, stomach, and oesophageal malignancies. It predicts a positive response to a monoclonal antibody, Herceptin/Trastuzumab, targeted against the HER-2/neu receptor.