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Mesothelioma

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Overview

Mesothelioma is a cancer that develops from the mesothelial lining of the lungs and is strongly associated with asbestos exposure. Other less common sites that can be affected are the lining of the abdomen, the pericardium, or the tunica vaginalis surrounding the testes.

Asbestos-Related Lung Diseases

Asbestos is a fibre-like material that was once used in insulating buildings. Its use has been fully banned since 1999. People exposed to asbestos often develop lung disease, and the risk of developing asbestos-related diseases increases with the duration and degree of exposure.

Asbestos exposure can lead to the development of:

  • Benign diseases:
    • Pleural plaques – most common
    • Pleural thickening
  • Interstitial lung disease:
    • Asbestosis – usually causes lower lobe fibrosis
  • Malignant disease:

Epidemiology

  • Mesothelioma is 3 times more common in men than in women
  • Around half of the cases are diagnosed in people >75 years
  • Incidence in the UK is around 3 per 100,000
  • Asbestos exposure accounts for the majority of cases 

Risk Factors

  • Asbestos exposure
  • Age >75 years – this is because the latency period between asbestos exposure and the development of mesothelioma is around 20-40 years, so most patients are older adults

Presentation

Mesothelioma should be suspected in a patient with new painless pleural effusions, especially if they have chest pain or a history of asbestos exposure. Patients may have:

  • Progressively worsening shortness of breath
  • Chest pain:
    • Usually due to the tumour spreading into the pleural lining
  • Cough:
    • Usually dry
  • Constitutional symptoms:
  • Reduced breath sounds on examination:
    • Usually due to pleural effusions or obstruction
  • Dullness to percussion on examination:
    • Usually due to pleural effusions

Differential Diagnoses

Small cell lung cancer

  • There may be haemoptysis, which is not typically seen in mesothelioma
  • The patient usually has a history of smoking
  • There may be features of paraneoplastic syndromes (e.g. ectopic ACTH secretion)

Non-small cell lung cancer

  • There may be haemoptysis, which is not typically seen in mesothelioma
  • There may be features of paraneoplastic syndromes (e.g. gynaecomastia in adenocarcinoma)

Investigations

All patients

  • Chest x-ray:
    • May show pleural effusions or pleural thickening
    • There may also be signs of asbestos exposure e.g. lower zone lung fibrosis
  • CT chest with contrast:
    • More sensitive for identifying mesothelioma
  • Pleural fluid analysis:
    • If a pleural effusion is present, the fluid should be sent for microscopy, culture and sensitivities, biochemistry, and cytology
  • Pleural biopsy via thoracoscopy
    • Allows for histological diagnosis

Diagnosis

Diagnosis is made based on clinical features and investigations. Lung cancer can be staged using the TNM classification system.

Management

Overview

Management currently is mainly symptomatic and palliative, unless the disease is extremely localised, then surgery may be considered. Chemotherapy and radiotherapy are other options that may be used.

Complications

  • Metastases

Prognosis

  • Survival for patients with malignant mesothelioma is around 1 year
  • Malignant mesothelioma almost always leads to death

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