PDGFRB and gastrointestinal stromal tumor: PDGFR Gain-of-function mutations are identified in PDGFRA in several diseases such as Y266C, Ins450C, Del (8,9), V536E, Ins544V, N659X, D842X, and Ins491A in glioblastoma; D842X, N659X, and V561D in GIST.