FLT4 and neoplasm: In the context of oncology, several PTKs directly regulate tumor angiogenesis including fibroblast growth factor receptor (FGFR), platelet-derived growth factor receptor (PDGFR), and vascular endothelial growth factor receptor (VEGFR) which has three isoforms; VEGFR-1 (Flt-1), VEGFR2 (KDR), and VEGFR-3 (Flt-4) [23].