Epidemiology

Mesothelioma presents at a median age of 60 years, typically 20–50 years after asbestos exposure and affects men five times more than women. Risk has been estimated to be linearly proportional to the intensity and duration of exposure. Latency periods between first exposure to asbestos and a diagnosis of mesothelioma may therefore vary by occupation, with shorter intervals for insulators and dock workers and longer intervals for shipyard and maritime workers, as well as domestic exposures.

A significant proportion of patients with mesothelioma diagnosed between the ages of 20 and 40 report household or neighbourhood exposure during childhood. Children who present with the disease generally have no apparent asbestos exposure. Despite increasing awareness of the role of asbestos in these tumours and measures to reduce asbestos exposure, it is estimated the incidence of mesothelioma will continue to rise until 2020.

Aetiology

Malignant mesothelioma is a rare tumour (<1% of cancers) that is highly aggressive, arising primarily from the surface serosal cells of the pleural, peritoneal and pericardial cavities. Exposure to asbestos fibres is the primary cause, although 50% of patients have no history of exposure. The risk is greatest with blue asbestos (crocidolite) then brown asbestos (amosite) and least with white asbestos (chrysolite).

In 60–83% of human malignant mesotheliomas the cells contain and express SV40 DNA, suggesting a possible co-factor. The exposure to asbestos fibres can produce reactive oxygen species when hydrogen peroxide and superoxide react to form hydroxyl radicals, which can induce DNA damage.

Clinical presentation