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Mixed progress against lung cancer

Although tobacco smoking causes many diseases and affects most of the organ systems in the body, lung cancer is typically the first condition that comes to mind when one considers the health impact of smoking. Lung cancer is also one of the most important and devastating illnesses caused by smoking, given its high incidence in populations where smoking is common, its high fatality rate, and the difficulty in detecting the disease when it is still localised. Therefore we commissioned an update on lung cancer and smoking from Dr Michael Thun of the American Cancer Society, which appears below.

Shown on the cover of this issue of “Tobacco Control” are four false-colour scanning electron micrographs of lung cancer, obtained from the Science Photo Library in London ( http://www.sciencephoto.com ). The upper left image shows cancer of the human bronchus, the most common form of lung cancer. Until the 1970s, such cancers usually occurred near the division of the trachea or large bronchi into smaller bronchi, because this area suffers from heavy deposition of the carcinogenic tars from high tar cigarettes. However, squamous carcinomas in large airways have now become less common than adenocarcinomas in small, peripheral airways, paralleling the shift from “high” to “medium” and “lower” yield cigarettes, the smoke from which is inhaled more deeply. The disorganised region of malignant tumour cells at the bottom right of this image is seen invading the normal, ciliated epithelium (or lining) of the bronchus at the left and top. Cancers consist of primitive cells which have not developed any function, such as the cilia of normal, bronchial epithelial cells. (The cilia are small, hair-like projections used to sweep mucus, debris, and microorganisms out of the lung.) 

The upper right image shows a tiny lung cancer (orange) filling an alveolus (one of the blind-ended air sacs …