Test Details: Immunohistochemical testing helps to identify specific antigens (proteins) within tissue sections utilizing an antigen-specific antibody. Estrogen and progesterone play key roles 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.