{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"HER2 /ErbB2 is one of four members of the ErbB receptor family of transmembrane receptor-like tyrosine kinases .The kinase activity of ErbB2 can be activated without a ligand if it is overexpressed, and by association with other ErbB proteins."}]},{"type":"paragraph","children":[{"type":"text","value":"HER2 is overexpressed in 25–30% of all breast cancers, including primary as well as metastatic breast tumors. HER2 has been widely investigated as a prognostic indicator."}]}]}