 Human epidermal growth factor HER2 is a receptor tyrosine kinase and regulates diverse functions in normal cells such as growth, differentiation and survival of cells. In 25-30 per cent of breast cancer HER2 gene is amplified, what result in abnormally high levels of encoded HER2 protein in malignant cells. Overexpression or amplification of HER2 is associated with an aggressive form of breast cancer seen by significantly shortened disease-free survival and overall survival. 