1 Clinicopathologic Considerations
The pathology of mesothelioma is classically biphasic with both epithelioid and sarcomatoid areas present. Monophasic tumours exist and pure epithelioid lesions can be difficult to differentiate from peripheral anaplastic lung carcinomas or metastatic carcinomas. Special stains reported to be most useful include calretinin, CK5/6, WT-1, and D2-40, while TTF-1, CEA, BerEP4, CD15 and B72.3 may help with the differential diagnosis. Histologic appearance appears to be of prognostic value, with most clinical studies showing that epithelioid mesotheliomas have a better prognosis than fibrous or sarcomatoid mesotheliomas.
2 Diagnostic Procedures
The chest radiograph usually shows a pleural effusion or pleural thickening. Computed tomography delineates the extent of disease far more accurately than chest radiography.
As many patients with mesothelioma present with a pleural effusion, they usually undergo thoracentesis and pleural fluid pathology is positive in about one third of cases. It is difficult to differentiate metastatic adenocarcinoma from mesothelioma with cytology alone. If the pleural space is totally or partially free, thoracoscopy is a very good approach to diagnosis because it commits the patient to a very limited surgical procedure, allows direct examination of clinically abnormal tissues and provides the pathologist with a good specimen obtained from an involved area. If the pleural space is obliterated by adhesions or tumour, diagnostic limited thoracotomy may be required.
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Boutin C, Rey F: Thoracoscopy in pleural malignant mesothelioma: a prospective study of 188 consecutive patients. Cancer 1993;72:389-393.