Lung Cancer

Most lung cancers start in the lining of the bronchi, the tubes which branch from the trachea into the lungs. But cancer can also begin in other areas — the trachea, bronchioles or alveoli. Lung cancers are thought to develop over a period of many years. First, there may be areas of precancerous changes in the lung. These changes do not form a mass or tumor. They cannot be seen on an x-ray and they do not cause symptoms. However, if these changes progress to true cancer, malignant (cancer) cells begin to grow. The cancer cells may produce chemicals that cause new blood vessels to form nearby. These new blood vessels nourish the cancer cells, which can continue to grow and form a tumor large enough to see on x-rays. Cells from the cancer can break away from the original tumor and spread to other parts of the body in a process called metastasis. Lung cancer is a life-threatening disease because it often spreads in this way.

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