[A study of lung cancer with presence of pleural effusion at the time of thoracotomy--cytologic evaluation of a relatively small amount of pleural effusion and prognosis after removal].

The cytologic evaluation of a relatively small amount of pleural effusion in lung cancer at the time of thoracotomy has not been previously considered, and prognosis after removal has not been clarified. In order to clarify these points, 99 cases of removed lung cancer with presence of pleural effusion at the time of thoracotomy were examined following cytology. Our study was conducted with regard to the amount and nature of pleural effusion, pleural effusion cytology, tumor development and its relation to prognosis. On the basis of this study a formula was developed relating the occurrence rate of cytologically positive pleural effusion with the development of tumor employing multivariate analysis, specifically the multiple regression analysis. 21% of these cases showed cytologically positive pleural effusion, indicating an absence of its correlation to the amount of pleural effusion; the conducting of cytology regardless of the amount of pleural effusion was found to be significant in determining the precise stage. The occurrence rate of cytologically positive squamous cell carcinoma was significantly few compared with those in other cell types. Regarding the pleural effusion of a relatively small amount, the prognosis after removal showed a relatively high three-year survival rate of 32% for those cases with negative pleural metastasis despite the positive showing of pleural effusion cytology, indicating the viability of surgery. From the occurrence rate of cytologically positive pleural effusion (Y) and the degree of pleural metastasis (X1)/the degree of pleural invasion (X2)/the degree of lymph nodes metastasis (X3), the following formula was obtained employing multiple regression analysis: Y = 0.344X1 + 0.050X2 + 0.034X3 + 0.075 (proportion 0.840).(ABSTRACT TRUNCATED AT 250 WORDS)