Test Details: Immunohistochemical testing is carried out on resected tissue specimen. This testing helps to identify specific antigens (proteins) within tissue sections utilizing an antigen-specific antibody. Estrogen and progesterone play a key role in a woman's sexual development and reproductive functions. Over-expression of Estrogen receptor (ER) and Progesterone receptor (PR) is seen in tumours of female sex steroid hormone responsive tissues such as the breast, endometrium, and ovary. ER/PR status predicts response to hormonal therapy and is a prognostic marker for survival in breast cancer patients. Positive steroid hormone status has predicted favourable overall survival independently of hormonal treatment. HER2/neu is protein involved in normal cell growth. Over-expression of HER2/neu is associated with poor prognosis of breast, ovarian, bladder, pancreatic, stomach, and oesophageal malignancies. It predicts for a positive response to a monoclonal antibody, trastuzumab, targeted against the HER2/neu receptor.