The relationship between increased clotting and malignancy is well recognized, though the bidirectional development of this association is often overlooked. In the challenging cancer biology, transforming genes often act in concert with numerous epigenetic factors, including hypoxia, inflammation, contact between blood and cancer cells, and emission of procoagulant vesicles from tumors, to determine a net imbalance of the hemostatic potential which is detectable by a variety of laboratory tests. Procoagulant factors, in particular, are intimately involved in all aspects of hemostatic, cell proliferation and cellular signalling systems. However, the biggest as yet unresolved question is why cancer patients develop thrombosis? Since the thrombus itself does not apparently contributes directly to the tumor biology, enhanced hemostasis activation in cancer patients may be interpreted according to the most recent biological evidences. Coagulation and cancer biology interact bidirectionally in a "vicious cycle", in which greater tumor burden supplies greater procoagulants (tissue factor, cancer procoagulant) and thrombin, which would in turn act as strong promoters of cancer growth and spread. In this perspective, thrombosis may be interpreted as a epiphenomenon of an intricate an effective biological feedback to maintain or promote cancer progression. In this review article, we briefly analyze the pathogenesis, laboratory, clinical and therapeutic features of cancer and thrombosis.