Immunocytochemical diagnosis of oat-cell carcinoma in pleural effusion.

Immunocytochemical studies were performed in order to accurately recognize the origin of tumor cells in a pleural effusion from a patient with a mediastinal mass. The immunoalkaline phosphatase technique was employed to examine several cell-specific surface antigens via their specific monoclonal antibodies. The tumor cells in this case did not have any demonstrable antigens of the human blood cells but did have abundance of an antigen specific for the tumor cells of oat-cell carcinoma. This diagnosis obtained by the immunochemical studies was confirmed by both cytologic and clinical findings. Immunocytochemical studies may become a mainstay for specific cytodiagnosis in the future.