HER

Human epidermal growth factor receptor type2 (HER-2) was emerged as a molecular biomarker in breast cancer, as important as the estrogen-receptor (ER). It is located on chromosome 17q and is a member of the type I growth factor receptor family. In breast cancer, HER-2 is over-expressed in 20%–30% of primary tumors. The clinical behavior of human breast cancer associated with this gene was originally demonstrated in 1987 . According to the initial report, HER-2 gene amplification could independently predict the time of disease relapse and overall survival in breast cancer patients. Thus, this gene is considered as one of the prognostic factors for breast cancer. However, conflicting results were reported later. This may be partly because of differences in the methodologies used to determine HER-2 status. At present, HER-2 is not considered a definite and independent prognostic marker of breast cancer.