PDGFRA and gastrointestinal stromal tumor: Recently, the finding that gastrointestinal stromal tumours (GISTs) lacking c-Kit mutations harbour intragenic activating mutations in PDGFR-α [6,7], and that ligand-independent constitutive activation can be blocked by means of a tyrosine kinase inhibitor (imatinib mesylate), has increased the interest for PDGFR-α as a target for therapy.