HER2 stands for human epidermal growth factor receptor 2. It is a gene that makes a protein found on the surface of all breast cells. It is involved in normal cell growth.
Genes are the basic units of heredity, passed down from your mother and father. In certain cancers , especially breast cancer , the HER2 gene mutates (changes) and makes extra copies of the gene. When this happens, the HER2 gene makes too much HER2 protein, causing cells to divide and grow too fast.
Cancers with high levels of the HER2 protein are known as HER2-positive. Cancers with low levels of the protein are known as HER2-negative. About 20 percent of breast cancers are HER2-positive. HER2 positive cancers tend to grow and spread faster than other types of breast cancer. But treatments that specifically target HER2-positive breast cancer can be very effective.
HER2 testing looks at a sample of tumor tissue to find out whether you have HER2-positive breast cancer.
Other names: human epidermal growth factor receptor 2, ERBB2 amplification, HER2 overexpression, HER2/neu tests