Although the majority of GIST carry a sensitive primary KIT mutation, about 5% to 10% of cases harbor activating mutations of PDGFRA, mainly involving the A-loop encoded by exon 18 (~5%), or more rarely the JM domain, encoded by exon 12 (~1%), or the ATP binding domain encoded by exon 14 (<1%) (Figure 1) [6]. This evidence concerns the gene PDGFRA and gastrointestinal stromal tumor.