The most common sites for mutations in GIST are in the juxtamembrane domain (exon 11; 60–70%) and the extracellular domain (exon 9; 5–10%) of KIT; mutations in PDGFRA (5–10%) are most commonly located in the activation loop (exon 18) and the juxtamembrane domain (exon 12) [3–6]. The gene discussed is KIT; the disease is gastrointestinal stromal tumor.