Mesothelioma accounts for less than 1% of all cancers in England, Wales and Northern Ireland. There are almost 2,500 new diagnoses a year, of which 96% are pleural. The median age at diagnosis for malignant pleural mesothelioma (MPM) is 76 years. The majority of cases occur in men, most commonly following occupational exposure to asbestos. There is a latent period, usually 30-40 years, between exposure and disease development. A chest X-ray is usually the first-line investigation; 94% of patients with MPM have a unilateral pleural effusion, although the chest X-ray may be normal or show another asbestos-related lung disease.