Medicine – Mesothelioma

Malignant mesothelioma is an aggressive cancer arising from the mesothelial lining of serosal surfaces, most commonly the pleura. Pleural mesothelioma is strongly associated with previous asbestos exposure and typically appears only after a very long latent period.

1. Malignant Tumour of the Pleura

The most common form is malignant pleural mesothelioma, which develops from the mesothelial cells lining the pleural cavity.

The tumour tends to spread diffusely along the pleural surface, causing irregular pleural thickening and encasement of the lung rather than forming a single discrete mass.

2. Association with Asbestos

A large proportion of pleural mesothelioma cases are related to previous asbestos exposure.

Older teaching often quotes a figure of about 85%, although the exact proportion varies between populations and occupational settings.

Unlike lung cancer, the risk of mesothelioma is not substantially increased by cigarette smoking.

3. Occupational and Secondary Exposure

Mesothelioma has historically been most common in men, reflecting greater occupational exposure to asbestos in industries such as shipbuilding, construction, insulation work, mining, and manufacturing.

However, disease can also occur in people with secondary household exposure. A classic example is a family member who repeatedly handled or washed asbestos-contaminated work clothes.

4. Crocidolite Exposure

Among the major asbestos fibre types, crocidolite, or blue asbestos, has traditionally been regarded as one of the most strongly associated with mesothelioma.

Its long, thin fibres can penetrate deeply into the lungs and pleura and remain within tissues for many years.

5. Long Latency Period

Mesothelioma usually develops only after a prolonged interval following asbestos exposure.

The latency period is commonly 20–50 years or longer, which means patients may present decades after the original occupational or environmental exposure has ended.

6. Clinical Presentation

Patients often present with progressive breathlessness, chest pain, weight loss, fatigue, and recurrent pleural effusions.

The pleural effusion is often unilateral, and the expanding pleural tumour can progressively restrict the affected lung.

7. Imaging

Chest radiography may show unilateral pleural effusion, pleural thickening, and reduced volume of the affected hemithorax.

CT is more useful for demonstrating nodular pleural thickening, pleural masses, involvement of the mediastinal pleura, and encasement of the lung.

8. Diagnosis

Definitive diagnosis usually requires tissue biopsy, often obtained thoracoscopically.

Pleural fluid cytology alone may be insufficient because malignant cells are not always detected in the effusion.

9. Prognosis

Malignant mesothelioma generally has a poor prognosis because it is often advanced at the time of diagnosis and tends to spread extensively along the pleural surface.

Treatment may involve combinations of systemic anticancer therapy, radiotherapy, surgery in highly selected patients, and palliative measures such as management of recurrent pleural effusions.

Key Clinical Pattern

Think of malignant pleural mesothelioma in a patient with a history of asbestos exposure decades earlier who presents with progressive breathlessness, chest pain, weight loss, and a recurrent unilateral pleural effusion.

The key association is asbestos exposure with a very long latency period, and crocidolite (blue asbestos) is classically considered particularly carcinogenic.