Thrombocytosis in patients with malignant pleural mesothelioma

Platelet counts were studied retrospectively in a series of 64 patients suspected of primary malignant pleural mesothelioma. Only platelet counts taken before chemotherapy and radiotherapy and surgery other than thoracocentesis were considered. Thirty-two patients had malignant pleural mesothelioma and 32 patients had other malignant disease in pleura. In both groups 34% had slightly elevated platelet counts. In a subgroup consisting of 18 patients with primary pulmonary adenocarcinoma 28% had thrombocytosis. The distribution of platelet counts did not differ in the diagnostic subgroups, and thrombocytosis had no differential diagnostic value in patients with malignant disease in any stage in the pleurae. The frequency of thromboembolic episodes was low.