[Cytodiagnosis and marker determination in pleural effusion]

Malignant cells can be identified in 70-85% of all tumor-induced serous effusions by cytological examination. Carcinoma and malignant lymphoma can be frequently found in pleural fluids, while sarcoma is rare. In many cases, morphological criteria allow these tumors to be distinguished and may even lead to identification of the primary site of carcinoma. This may be of considerable therapeutic relevance. It may however be impossible to classify undifferentiated tumors on the basis of morphology alone. In these cases a diagnosis may be established by immunocytochemical typing. The most commonly employed markers and their applications are discussed.