HER2

HER2 1 Human epidermal growth factor receptor. 2 A protein involved in normal cell growth that is found in abnormally high levels on, and promotes the growth of, some cancer cells, notably breast cancer cells. HER2-positive breast cancers tend to be more aggressive than other types of breast cancer and are less responsive to treatment with hormones. Treatments that target HER2, such as trastuzumab (Herceptin), can be effective in breast cancers that overexpress HER2. Breast cancer tissue is routinely tested for HER2 because the results may affect treatment recommendations and decisions. Also known as HER2/neu, c-erb-B-2. See also Herceptin.