PDPN and neoplasm: CAFs promote malignant transformation and tumor proliferation by the expression of cell surface markers such as surface-like alpha-smooth muscle actin (α-SMA), fibroblast activation protein (FAP), vimentin, fibroblast-specific protein 1 (FSP1), podoplanin (PDPN/gp38), and platelet-derived growth factor receptor alpha and/or beta (PDGFRα/β) and several chemokines, cytokines, growth factors, miRNAs, exosomes, and metabolites (Figure 1) [5].