In GISTs (KIT and PDGFRA mutations), breast carcinoma (HER-2 amplification) and lung cancer (EGFR mutation), targeted therapy has yielded best results in cases with activating mutation or amplification of the respective gene (Vogel et al, 2002; Heinrich et al, 2003; Lynch et al, 2004). The gene discussed is KIT; the disease is lung carcinoma.