PDGFRA and gastrointestinal stromal tumor: GIST is a kind of heterogeneous tumor that should be stratified to different risk levels, ranging from very low risk, low risk, intermediate risk to high risk, according to the tumor size, tumor location, and activity of mitosis.[17] IM, a small molecule inhibitor of the oncoprotein Kit and platelet-derived growth factor receptor alpha (PDGFRA), has been recommended to be the standard treatment for recurrent and metastatic GIST.