PDGFRB and gastrointestinal stromal tumor: Imatinib, a TK inhibitor targeting ABL, KIT and PDGFR, has shown impressive efficacy in gastrointestinal stromal tumors carrying gain-of-function KIT or PDGFRA mutations, and in dermatofibrosarcoma protuberans (DFSP) characterized by overactivation of PDGFR due to a collagen 1A1 (COL1A1)/PDGFB rearrangement [4, 5].