2. Morphological and immunohistochemical documentation of GIST (immunostaining for KIT/ (CD117) and/or DOG-1 (anoctamin-1)) must be positive on a tumour sample. Patients with demonstrated mutation in KIT or PDGFRA may be entered to the study despite negative immunostaining for KIT and DOG-1 provided that tumour histology is compatible with GIST.