Human epidermal growth factor receptor 2 (HER2) is a receptor located on the cell membrane of certain cells, involved in signal transduction (cellular signaling) to result in cell growth and differentiation. In some cancers eg some breast cancers and other cancers, the HER2 receptor is overexpressed facilitating the growth of the cancer. There are pharmacological agents that are directed against this receptor to inactivate it and slow/inhibit tumour growth.