{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Factor VIII-Related Antigen or von Willebrand factor (VWF) is a multimeric glycoprotein. It has functional binding domains to platelet glycoprotein Ib, glycoprotein IIb/IIIa, collagen and heparin. VWF is synthesized by endothelial cells and stored in the Weibel-Palade granules. It mediates platelet adhesion to injured vessel walls and serves as a carrier and stabilizer for coagulation factor VIII. According to literature, VWF is a useful marker to identify endothelial or megakaryocytic lineage of neoplasms. However, not all endothelial cells synthesize/store this molecule, some tumors of vascular origin fail to stain for VWF. Staining for VWF has also been used to measure angiogenesis, a process that has implications in tumor growth."}]}]}