PDPN and neoplasm: Lymphatic vascular density (LVD) is used as an evaluation index for lymphangiogenesis [34], in addition, various LECs-specific endothelial markers have been used to evaluate tumor-associated lymphangiogenesis by immunohistochemical methods, including Prox-1 [34], VEGFR-3 [35, 36], LVYE-1 [37], Podoplanin [34], D2-40 [38, 39], NRP-2 [40] and others (Fig. 1).