TF and breast neoplasm: TF is not expressed on the membrane of quiescent endothelial cells, but is present in vascular smooth muscle cells.7 Although breast tumour-associated endothelial cells have been observed to express TF,30 this finding was not independently confirmed31 and, to our knowledge, has not been unequivocally established in the case of endothelial cells associated with pancreatic tumours.