HER-2

HER-2 stands for Human Epidermal Growth Factor Receptor 2.  The HER-2 gene is one of thousands of genes that comprise every living person's genetic code and is present in the nucleus of all human cells, including breast tissue cells.  The HER-2 gene provides the blueprint for the manufacture of the HER-2 protein.  This protein, which is attached to the cell membrane, regulates normal cell growth and function. 

Abnormally high quantities of the HER-2 gene have been associated with rapid tumor cell growth, resistance to therapy, and shorter disease-free periods and overall survival.  Approximately 20-25%, or 1 out of every 4, breast cancers have an abnormally high quantity of the HER-2 gene, and are considered HER-2 positive.