What Is Lung Cancer? |
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The lungs are two sponge-like organs found in the chest. The right lung is divided into three sections, called lobes. The left lung is smaller, only having two lobes, because the heart takes up more room on that side of the body. When breathing, air goes into the lung through the trachea (windpipe). The trachea divides into tubes called the bronchi, which then subdivide into smaller tubes called the bronchioles. At the end of the bronchioles are tiny air sacs called alveoli. Tiny blood vessels run through alveoli where they absorb oxygen into the blood stream and release carbon dioxide to be exhaled. The lungs are lined with the pleura. The pleura protects the lungs and helps their sliding motion as they expand and contract during breathing.
Most lung cancers start in the lining of the bronchi tubes. Cancers begin less often in the trachea, bronchioles, or alveoli. Lung cancers develop over a period of many years. There may be areas of precancerous changes in the lung, but these changes do not form a mass or tumor that can be seen on an x-ray. These changes also do not cause any symptoms. They can be found by analyzing cells in the lining of the airways of the lungs. Molecular abnormalities recently believed to be precancerous have been identified in cells from individuals at high risk to develop lung cancers (such as survivors from prior lung cancers). These precancerous changes often progress to true lung cancer. As the cancer develops, the cancer cells may produce chemicals that cause new blood vessels to form near the area. These new blood vessels provide nourishment to the cancer cells, which can then form a tumor large enough to see on an x-ray. Cells from the cancer area can break off and be carried through the bloodstream from the original tumor and spread to other parts of the body. This is called metastasis.
Lung cancer is a life-threatening disease because it often spread to other parts of the body before it can be detected on a chest x-ray.
