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 SCLC pleural 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.