SPP1 and neoplasm: In PTTM, tumor emboli in pulmonary vessels may not only damage the endothelium but also activate the coagulation systems and release inflammatory mediators and growth factors, including tissue factor, vascular endothelial growth factor (VEGF) [5], platelet-derived growth factor (PDGF) [6], and osteopontin [7], which induce fibrocellular intimal proliferation.