Pleural mesothelioma is associated with-

Malignant mesothelioma of pleura Malignant mesothelioma in the thorax arise from either the visceral or the parietal pleura. It is associated with exposure to asbestos. Simian virus 40 (SV40) viral DNA has also been associated with malignant mesothelioma. Morphology Malignant mesothelioma is a diffuse lesion that spreads widely in the pleural surface and is usually associated with extensive pleural effusion and direct invasion of thoracic structures. Malignant mesothelioma may be of following types, depending on the type of mesothelial cells that is present in the tumor. 1. Epithelioid type Mesothelial cells develop as epithelium like lining cells. Consists of cuboidal, columnar or flattened cells forming tubular or papillary structures. Epithelioid type of mesothelioma resembles adenocarcinoma of lung and can be differentiated from it by following featurs:- Positive staining for mucopolysaccharide. Lack of staining for carcinoembryonic antigen (CEA). Strong staining for keratin. Positive staining for calretinin, wilms' tumor 1 susceptibility gene product, cytokeratin 5/6, mesothelin and thrombomodulin. Presence of long microvilli and abundant tonofilaments but absent microvillous rootlets and lamellar bodies. 2. Sarcomatoid (mesenchymal type) Mesothelial cells develop as mesenchymal stromal cells. They appear as spindle cell sarcoma, resembling fibrosarcoma. 3. Mixed type (Biphasic type) Contains both epithelioid and sarcomatoid patterns.