We report a case of granulocytic sarcoma of the bone with pleural involvement diagnosed upon cytologic analysis of the pleural fluid (centrifugation spots stained by May-Grunwald-Giemsa) and confirmed by more complex investigations, i.e., demonstration of granulomonocytic membrane antigens by immunohistochemical monoclonal antibody techniques on frozen sections of the tumor. This case draws attention to the value of cytologic studies in granulocytic sarcomas whose histologic features are suggestive of lymphoma.