PDGFRA and gastrointestinal stromal tumor: Gastrointestinal stromal tumor (GIST) is the most common sarcoma arising in the GI tract and shares features with the interstitial cell of Cajal, the pacemaker cell of the GI tract.1,2 Most GISTs encode activating mutations in either the kit or platelet-derived growth factor receptor-α (PDGFR-α) gene, an important genetic event in tumorigenesis.3,4