PDPN and neoplasm: P-selectin on the platelet surface binds to the Sialyl-Lewisx-tetrasaccharide conjugate of PSGL-1 (P-selectin glycoprotein ligand-1) expressed on tumor cells, thus constituting a secondary level of platelet-tumor cell cohesion downstream of the Clec-2-podoplanin interaction (Coupland and Parish, 2014).