Lung Cancer
For many years, lung cancer was more prevalent in men than in women, but recently, it has surpassed breast cancer as a cause of death in women. This can be linked to an increase in the number of women who smoke today. Autopsies on smokers have revealed the progressive steps by which the most common form of lung cancer develops. The first event appears to be thickening and callusing of the cells lining the bronchi. (Callusing occurs whenever cells are exposed to irritants.) Then, a loss of cilia makes it impossible to prevent dust and dirt from settling in the lungs. Following this, cells with atypical nuclei appear in the callused lining. A tumor consisting of disordered cells with atypical nuclei is considered to be cancer in situ (at one location). A final step occurs when some of these cells break loose and penetrate other tissues, a process called metastasis. Now the cancer has spread. The tumor may grow until the bronchus is blocked, cutting off the air supply to that lung. The entire lung then collapses, the secretions trapped in the lung spaces become infected, and pneumonia or a lung abscess (localized area of pus) results. The only treatment that offers a possibility of cure is to remove a lobe or the lung completely before secondary growths have had time to form. This operation is called pneumonectomy.
The incidence of lung cancer is over 20 times higher in individuals who smoke than in those who do not. In addition, current research indicates that passive smokingsimply breathing in air filled with cigarette smoke-can also cause lung cancer and other illnesses associated with smoking. If a person stops smoking, and if the body tissues are not already cancerous, they usually return to normal over time.
Acute bronchitis pneumonia and tuberculosis are caused by bacteria. Chronic bronchitis. emphysema. and lung cancer occur more frequently in smokers than in nonsmokers.
