Tissue factor (TF) is an essential enzyme activator that forms a catalytic complex with FVII(a) and initiates coagulation by activating FIX and FX, ultimately resulting in thrombin formation. TF is found in adventitia of blood vessels and the lipid core of atherosclerotic plaques. In unstable coronary syndromes, plaque rupture initiates coagulation by exposing TF to blood. Alternative splicing of TF pre-mRNA yields alternatively spliced TF (asTF). asTF lacks the transmembrane domain and can thus be secreted. In humans and mice, asTF contains a novel C-terminus with poor homology to any known proteins. High expression of asTF expression in tumor cell lines suggests a role in tumor progression. Subcutaneous growth of pancreatic cancer cells overexpressing asTF, results in larger and more vascularized tumors. asTF facilitate cellular signaling via distinct mechanisms critical to tumor cell behavior.