Granulocytic sarcoma with pleural involvement. Identification of neoplastic cells with cytochemistry.

Malignant cells were detected in the pleural effusion of a patient with three separate primary malignancies. These cells were judged by conventional morphologic studies to be poorly differentiated cells, but cytochemical studies showed them to be granulocytic precursor cells. The use of cytochemical or immunochemical techniques may be most practical for the cytodiagnosis of malignant cells in serous effusions.