HER2, or human epidermal growth factor receptor 2, is a protein that is encoded by the HER2 gene. It is a member of the epidermal growth factor receptor family and plays a crucial role in cell growth and division. Abnormalities in the HER2 gene, such as gene amplification or protein overexpression, have been associated with certain types of cancer, particularly breast cancer. Research in the area of HER2 focuses on understanding its role in cancer development and progression, as well as developing targeted therapies to treat HER2-positive cancers. These therapies, such as HER2-targeted monoclonal antibodies and small molecule inhibitors, have significantly improved the prognosis and treatment outcomes for patients with HER2-positive breast cancer.