Such wild-type GISTs are now known to be heterogeneous and may actually possess mutations in the SDH complex genes, NF1, BRAF, NRAS, or HRAS. Imatinib mesylate, a selective tyrosine kinase inhibitor of KIT, PDGFR-α, and Abl, exhibits exceptional activity in advanced GIST patients. This evidence concerns the gene PDGFRA and gastrointestinal stromal tumor.