PDGFRB and cholangiocarcinoma: Sorafenib is an oral inhibitor of vascular endothelial growth factor receptors 2 and 3 (VEGFR-2/3), platelet-derived growth factor receptor β (PDGFR-β), and oncogenic kinases KIT, B-RAF, and C-RAF, that has shown a limited effect in advanced CCA as a single agent [42,43].