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Definition of HER2
Medically reviewed by Min Clinic Staff | Updated: January 2026
HER2: Abbreviation for human epidermal growth factor receptor 2. HER2 is a transmembrane tyrosine kinase receptor and is expressed by, and involved in the growth of, some cancer cells. For example, HER2 is overexpressed in 18% to 20% of invasive breast cancers and affects treatment as well as prognosis of breast cancers.
Also called c-erbB-2 or neu; also written HER-2.