Malignant pleural diseases.

The incidence of malignant pleural effusions has been increasing over the last few decades (mainly due to the absolute increase in several types of cancers, especially those of lung and breast origin) and they account for up to 50% of the exudates in many clinical series. Although pleural malignancies are thought to present most frequently with a pleural effusion, several autopsy series, including the current one, found a pleural effusion present in little more than half of the cases of malignant pleural involvement (55% in this series). Thus, many pleural malignancies without effusion might pass unnoticed in clinical practice, especially in metastatic disease. Primary malignancies of the pleura (mesotheliomas) are associated with asbestos exposure in about two-thirds of cases, and they frequently present with chest pain, sometimes associated with a pleural effusion. Benign pleural plaques can coexist with malignant mesothelioma, and this association should be suspected when long-standing plaques change in shape or size over the years, and especially if chest pain develops in a previously asymptomatic patient. Metastatic pleural involvement is much more frequent than mesotheliomas, and its most frequent mechanism is the vascular spreading of tumour cells from distant organs to the lungs, and on to the visceral and parietal pleura. The visceral pleura was involved in up to 87% of the current metastatic cases, whereas the parietal zone in only 47% of the autopsy series. The diagnostic work-up lies in cytology, whose average yield is approximately 50%, and a biopsy technique (either by blind needle biopsy or thoracoscopy) is recommended when the effusion persists, for > 2 weeks, and the first cytology has been negative. Thoracoscopy has the additional advantage of allowing pleurodesis with talc poudrage if clear tumour lesions are found in the pleura. In cases of malignant effusion which are not sensitive to chemotherapy, pleurodesis is the treatment of choice for palliation of symptoms, and talc is the most effective agent. It can be used either in suspension ("slurry") or in dry aerosolized form ("talc poudrage"), but it seems that this last technique achieves the best effects. However, it requires thoracoscopy for a proper application, and this is its main drawback when that technique is not readily available.