PGF and neoplasm: The VEGF receptor pathway is crucial in tumour angiogenesis and consists of 5 related ligands, namely placental growth factor (PlGF), VEGF A, VEGF B, VEGF C, and VEGF D which differentially bind to three receptor tyrosine kinases (VEGF R1, VEGF R2, and VEGF R3) [11,29,30,31].