Abstract
Under certain circumstances, relatively large lymphocytes which have irregular shaped nuclei and are inversion of the nucleus-cytoplasm relationship appear with very high frequency in the pleural cavity effusions of some patients with malignancy or chronic diseases. They proved to be T lymphocytes by morphological, immunological and cytochemical examinations. Proportions of T lymphocytes of the pleural cavity effusions were extremely higher than those of peripheral blood. However thoracic duct lymph contains almost 100% T lymphocytes. T lymphocytes of the pleural cavity effusions may leak from the thoracic duct and/or branches because of contraction, occlusion, or injury of the thoracic duct as a of result pressures of malignant tumor etc.
