Immunocytochemical profile of malignant pleural effusions of small-cell lung cancer.

Background. Small-cell lung carcinoma (SCLC) is a highly malignant tumour of a somewhat distinctive cell type. The aim of this study was to determine the immunocytochemical profile of tumor cells and lymphoid cell in SCLCpleural fluids. Methods. Nine cases of malignant pleural fluids of SCLC were studied using cell block preparation. In pleural effusions cytologically proven to be malignant in 9 patients with SCLC, the immunocytological features of tumor cells, together with the determination of lymphocytic subsets were documented. Results. In all 9 cases, tumor cells reacted with neuron-specific enolase (NSE) (100%), whereas in 6 of 9 cases (66,66%) tumor cell expressed synaptophysin, thyroid transciption factor-1 (TTF-1) and chromogranin A antigens. Phenotyping of the lymphocytes revealed in the majority of cases an expression of CD3 and CD4 antigens (8 and 7 cases, respectively) in contrast to CD8 and CD20 expression (1 and 1 case, respectively). Conclusions. The reactivity pattern of the tumor cells with the markers used in our study is a specific for SCLC. No significant difference in the distribution of lymphocytic subpopulations is observed in correlation with other malignant and no malignant processes involving the pleural cavity.