Megakaryocytes in the Pulmonary Circulation

The streptolysin 0 hemolysis method for isolation of cancer cells in the blood was employed for direct observations of the incidence and some characteristics of circulating megakaryocytes. In a series of 168 patients, circulating megakaryocytes were found in 77 per cent of the blood samples. Each sample contained an average of 1.2 megakaryocytes per ml. of blood. The megakaryocytes were most frequent in pulmonary arterial blood and a number of the cells had an apparently intact abundant cytoplasm. Pulmonary venous blood contained megakaryocytes much less frequently. These were almost always without cytoplasm or with only a narrow rim of it and as a rule small naked nuclei or their fragments were found. Manipulation of lung tissue resulted in an increased amount of megakaryocytes in the pulmonary venous blood. The megakaryocytes in pulmonary and systemic circulation were more numerous in advanced malignant disease than in early cases, and more common in inflammatory disease or severe anemia than in other nonmalignant disease.