Breast cancer usually has indicators in the middle of immunohistochemistry, such as negative or positive estrogen receptor ER, progesterone receptor PR and human epidermal growth factor receptor 2, with negative or positive HER-2. The reason for this is that different groups of breast cancer patients may contain different receptors. If a patient has estrogen and progesterone receptors, that is, if they show ER and PR positivity on immunohistochemistry, this suggests that anti-estrogen therapy, or endocrine therapy, is effective. Also if the body contains human epidermal growth factor receptor 2, HER-2 antibodies that is, targeted therapy, Herceptin can be applied. Of course there are times when HER-2 is not overly amplified and further genetic testing is needed to understand if there is over-amplification before deciding whether targeted therapy can be used. So a negative or positive immunohistochemistry test is used to guide further treatment.