Pleural Mesothelioma

Malignant pleural mesothelioma is the most common type of mesothelioma, making up over two-thirds of all cases. Pleural mesothelioma affects the lining of the lung and chest cavity known as the pleura.

The pleura is made up of the parietal and visceral pleura. The parietal pleura lines the chest wall and diaphragm while the visceral pleura lines the lungs.

Asbestos fibers work their way into the smallest passageways of the lungs and then into the pleura. Once there, an unknown chemical reaction causes cancerous cell development. As the cells begin to divide abnormally, the pleural lining thickens and excess fluid may accumulate. Pleural thickening gradually contracts the breathing space, causing shortness of breath—often the first symptom for pleural mesothelioma. The fluid, once carefully measured to allow smooth movement between the lungs and other organs, now causes increased pressure, further hindering breathing. This excess fluid is often seen on X-rays, and is referred to as a pleural effusion.

Pleural mesothelioma, like all kinds of mesothelioma, can be difficult to diagnose or easily misdiagnosed. If you are aware of prior asbestos exposure, it is important to inform your physician so that mesothelioma symptoms can be correctly identified.

• A mesothelioma is associated with exposure to asbestos, especially blue asbestos. A mesothelioma is a tumour of mesothelial cells which generally occurs in the pleura (rarely a mesothelioma may occur in the peritoneum or other organs)
  
   
• exposure may only be brief. There may be a lag-time of 20 to 40 years. Only approximately 20% of patients have pulmonary asbestosis - however about 90% of patients report previous exposure to asbestosis
  
   
• Investigations:
  • chest radiography/CT shows a pleural thickening and an associated pleural effusion. These abnormalities are usually unilateral
  • pleural biopsy is required for a certain diagnosis
  • staging
    • stageI: disease confined inside the capsule of the parietal pleura: ipsilateral pleura, lung, pericardium, and diaphragm
    • stage II: as described for stage I with intrathoracic (N1 or N2) lymph nodes
    • stage III: this signifies local extension of disease into the following: chest wall or mediastinum; heart or through the diaphragm, peritoneum; with or without extrathoracic or contralateral (N3) lymph node involvement
    • stage IV: this signifies distant metastases have occurred
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• this tumour is generally only appropriate for symptomatic treatment. Curative surgical treatment may be possible with stage 1 disease.
  • extrapleural pneumonectomy - this may lengthen time to recurrence
  • palliative pain relief and relief from pleural effusions may be mediated by pleurectomy and decortication
  • no evidence that radiotherapy or chemotherapy improves survival. Radiotherapy may help with pain management
    
     
• prognosis - depends on factors such as staging, histology, patient age. If extensive disease then median survival is approximately 5 months - local disease then approximately 16 months

Reference:

1. Lancet (1995), 345,1233-4.