Lung Cancer

Your lungs are two sponge-like organs found in your chest cavity. Your right lung is divided into 3 sections, called lobes. Your left lung has 2 lobes. It is smaller because your heart takes up more room on that side of the body. When you breathe, air goes into your lung through the trachea (windpipe). The trachea divides into tubes called the bronchi, which divide into smaller branches called the bronchioles. At the end of the bronchioles are tiny air sacs known as alveoli. Many tiny blood vessels run through the alveoli, absorbing oxygen from the inhaled air into your bloodstream and releasing carbon dioxide. Taking in oxygen and getting rid of carbon dioxide are your lungs’ main function. A slippery lining, called the pleura, surrounds the lungs. This lining protects your lungs and helps them slide back and forth as they expand and contract during breathing.

Most lung cancers start in the lining of the bronchi. That is why another term for lung cancer is bronchogenic cancer. Lung cancer can also form in glands below the lining of the bronchi, frequently in the periphery of the lungs. 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. But, these precancerous changes can be found by analyzing cells in the lining of the airways of smoke-damaged lungs.

Recently, molecular abnormalities believed to be precancerous have been identified in cells from individuals at high risk to develop lung cancers (for example, survivors from one prior lung cancer). These precancerous changes often progress to true cancer. As a cancer develops, 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. As noted earlier, this process is called metastasis.

Lung cancer is a life-threatening disease because it often spreads in this way even before it can be detected on a chest x-ray.