ABSTRACT
Carcinoma of the lung is the most common cause of malignant pleural effusion. The incidence of pleural effusion due to lung carcinoma was reported in 641 cases out of 1783 patients (36%), while the second most common cause was breast carcinoma in 449 cases (25%) (1). The incidence of pleural effusion in patients with lung carcinoma ranges between 7% (280 of 4000 cases) (2) and 23% (5,888 of 25,464 cases) (3). All histological types of bronchogenic carcinomas are likely to present pleural effusion (3). However, the most frequent histological type seems to be adenocarcinoma, in about 40% of the cases, as it is more likely to arise in the periphery next to the pleura, which may be invaded by the tumor. The second most common tumor is small-cell lung carcinoma, a tumor with highly invasive potential, accounting for about 25% of the cases (3, 4).
