Evidence for longer survival of patients with pleural mesothelioma without asbestos exposure

In a group of 23 patients with histologically confirmed malignant mesothelioma of the pleura who could not recall exposure to asbestos dust, survival was significantly longer than in a group of 83 patients with known exposure. Asbestos bodies were found by a quantitative method significantly less frequently in the unexposed than in the exposed group. The longer survival of patients without known exposure could not be correlated with any significant difference in the histological cell types of the tumours from those of exposed patients. In the 83 patients with known exposure survival did not relate to duration of exposure. Consequently, although the tumours of patients unable to recall exposure may be caused by unrecognised environmental contamination with asbestos dust, the longer survival of these patients would suggest a different aetiology.