FLT4 and neoplasm: The best validated signalling system for tumour lymphangiogenesis involves the secreted glycoproteins VEGF-C and VEGF-D that signal via VEGF receptor-3 (VEGFR-3; also known as Flt4), expressed on the surface of lymphatic endothelial cells (Joukov et al, 1996; Achen et al, 1998; Veikkola et al, 2001).