FLT4 and neoplasm: Actually, other than VEGF-C, VEGF-D and VEGFR-3, many other potent growth factors were involved in tumor lymphangiogenesis, such as VEGF-A, platelet-derived growth factor (PDGF), hepatocyte growth factor (HGF), angiopoietin (Ang)-1, Ang-2, insulin-like growth factor (IGF)-1 and basic fibroblast growth factor (bFGF), cyclooxygenase-2 (COX-2), and Slit2 [20, 24, 28, 32, 33, 37, 41, 46, 48, 57].