Diagnosis and prognosis in malignant pleural mesothelioma: a prospective study.

In a prospective study of 336 consecutive patients with long-term pleural effusions, 32 cases of malignant mesothelioma were found. Microscopic examination of pleural tissue specimens, preferably selected at thoracoscopy, proved superior to pleural fluid analysis as an aid to correct diagnosis. The epithelial proved to be the most common type of malignant mesothelioma. As an example of the mesothelial cells' multipotent ability, malignant cells were seen transforming into fat-like cells with lipid-containing vacuoles. In the fibrous tumour type, cytological examination of pleural fluid revealed only normal cells. Cells with malignant features were seen in fluid samples from epithelial and biphasic tumour types. The malignant cells often formed tubuli-like aggregates which could be mistaken for adenocarcinoma. Hyaluronic acid was more frequently detected in tissue specimens than in the pleural fluid samples. The morphological type and the patient's age had an impact on the survival time, whereas sex and extensive surgical treatment seemed less important.