TGFB1 and neoplasm: The interaction between platelet/fibrin and tumor cells promotes metastasis formation in different ways: (i) by providing a cover that protects the neoplastic embolus and possibly newly settled micrometastases from NK cell-mediated elimination [20]; (ii) by stimulating the extravasation through the upregulation of adhesion molecules and the increase in endothelial permeability [21,22,23]; and (iii) by preconditioning the “metastatic niche” with platelet-derived cytokines such as TGF-β [21].