PF4 and cancer: Poorly differentiated cancer always accompanied with elevated PLR, for that poorly differentiated tumour cells growing faster with angiogenic and tumour growth factors secreted by platelet cell, such as platelet factor 4 (PF4), thrombospondin, vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF-β) and platelet-derived growth factor (PDGF) [36].