PDGFRA and carcinoid tumor: In support of this hypothesis, Rossi et al demonstrated that LCNECs overexpress several RTKs, including KIT, the platelet-derived growth factor receptors α (PDGFRα) and β (PDGFRβ), and MET in a number of patients, whereas they failed to find a significant expression in other NSCLCs and carcinoids (32,34).