Several molecules, such as collagens, thrombin, ADP, and TBxA2, are known to induce platelet activation [17], and we previously discovered that podoplanin/Aggrus (PDPN), a type I transmembrane sialoglycoprotein expressed in several types of cancers, is a key molecule for tumor-induced platelet aggregation [41]. Here, PDPN is linked to cancer.