Lung cancer due to asbestos. Light micrograph of a section through a mesothelioma - a cancerous lung tumour caused by inhalation of asbestos dust. Mes- otheliomas develop on the pleural membrane outside the lungs, eventually growing to form a white mass that covers both lungs and obliterates the pleural cavity. The cancer cells seen here are a mixture of epithelial tissue (darker purple) and fibrous connective tissue (light pink). Variation in cell size, large cell nuclei (dark-staining) and disor- ganisation are all signs of malignancy. This form of cancer is difficult to treat and often fatal. Stained with hematoxylin and eosin. Magnification x125 at 35mm size.