Flamethrowers: blood cells and cancer thrombosis risk.

Cancer patients are at an increased risk of venous thromboembolism. The clotting system is activated in most cancer patients, which is reflected by specific parameters such as an increased thrombin generation and elevated D-dimer levels. Blood cells, especially WBCs and platelets, play an important role in this activation process. Neutrophils and monocytes are subpopulations of WBCs that increase the thrombotic potential by different mechanisms. Neutrophils are activated by tumor cells and can release DNA, generating highly thrombogenic neutrophil extracellular traps. Monocytes are able to synthesize and express significant quantities of procoagulant tissue factor on their surfaces upon activation. An increased risk of VTE has been found in patients with solid tumors and elevated platelet count and in those with high-grade gliomas and low platelet count. Small circulating membrane vesicles, also called microparticles (MPs), which largely derive from platelets, contribute to the procoagulant potential. Specifically, procoagulant MPs could play a role in tumor-associated thrombosis in pancreatic cancer. Interventional studies are under way that are investigating the benefits of thromboprophylaxis in patients identified to be at high risk of VTE through risk-scoring models that include blood count parameters. The "flames" thrown by blood cells, such as neutrophil extracellular traps and MPs, although exciting, still have to be investigated for their usefulness in the clinical setting.