OBJECTIVE: The aim of this study was to identify the participation of the coagulation system in the differential diagnosis of pleural effusions. INTRODUCTION: Imbalance between immunologic and metabolic factors triggers a sequence of events resulting in pleural reactions and accumulation of fluid. The coagulation system, which is fundamental for the maintenance of homeostasis, contributes to the inflammatory process responsible for pleural effusions, and participates in cellular proliferation and migration as well as in the synthesis of inflammatory mediators. METHODS: We evaluated the laboratory profile of coagulation and fibrinolysis in 54 pleural fluids (15 transudates and 39 exudates). RESULTS: The coagulation system acts according to the pathophysiologic mechanisms involved in the development of pleural effusions. In inflammatory effusions (exudates), there is activation of coagulation with increased levels of fragment 1+2 and thrombin-antithrombin complex in addition to reduction of fibrinogen levels due to fibrinolysis and fibrin tissue incorporation. As a consequence, there is activation of the fibrinolytic system with increased levels of fibrin degradation products, including the D-dimer. These changes are not sufficient for differentiation of different subgroups of exudates. In transudates, these events were observed to a lesser degree. CONCLUSION: The coagulation system plays an important role in the development of pleural diseases. Coagulation tests show differences between transudates and exudates but not among exudate subgroups. Understanding the physiopathological mechanisms of pleural disorders may help to define new diagnostic and therapeutic approaches.

A relação entre câncer e alteração na coagulação já havia sido sugerida há quase 150 anos por Trousseau e, subseqüentemente, ficou claro o maior risco que os pacientes oncológicos têm de desenvolverem fenômenos tromboembólicos. Isto pode ser conseqüência da ativação do sistema de coagulação pelas células neoplásicas ou pelas terapias empregadas (quimioterapias e cirurgias). Tais fenômenos podem, ainda, ser a primeira manifestação do câncer e a sua recorrência, mesmo com anticoagulação adequada, foi descrita. O sistema de coagulação é ativado, normalmente, com finalidade reparativa. Na presença de neoplasias, este complexo sistema está atuante frente a variados estímulos e parece contribuir para a progressão tumoral. Este efeito é mais importante para os focos metastáticos que para o próprio tumor primário. Contudo, a maior parte das vítimas de neoplasias morre das complicações das metástases, revelando a importância deste tema. Nesta área, vários mecanismos já são conhecidos e geram interessantes perspectivas para tratamentos futuros. Atualmente, o sucesso obtido com as heparinas de baixo peso molecular no carcinoma de pequenas células de pulmão é animador. Embora o conhecimento sobre esses mecanismos sejam relativamente recentes, os campos de pesquisa e tratamento estão amplamente abertos.

The relationship between cancer and coagulopathy was suggested by Trousseau nearly 150 years ago. Later, it became more evident that oncologic patients are at a higher risk of experiencing thromboembolic events. This can be due to activation of the coagulation system either by neoplastic cells or by prescribed therapies (chemotherapy or surgical procedures). In fact, these events can constitute the first manifestation of cancer, and their recurrence, despite efficient anticoagulation, has been described. The coagulation system is normally activated in order to provide healing. In the presence of neoplasms, this complex system is activated as a response to multiple stimuli and seems to contribute to cancer progression. Activation of the coagulation system has a greater effect on metastatic foci than on the primary tumor. However, most cancer victims die from complications caused by metastasis, which underscores the importance of this theme. In this area, various mechanisms have been described, creating promising perspectives for future treatments. The current success in using low-molecular-weight heparins against small cell lung cancer is encouraging. Although the knowledge of those mechanisms is relatively incipient, many basic research and clinical studies are underway.