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The lungs are sponge-like organs that are part of the respiratory system. During breathing, air enters the mouth or nasal passage and travels down the windpipe or trachea. The trachea splits into two sets of tubes, bronchial tubes, which lead to the left and right lung. The bronchi branch off into smaller and smaller tubes that eventually end in small balloon-like sacs called as alveoli. The alveoli are where oxygen, carbon dioxide, and other substances are exchanged between the lungs and the blood stream.
The lungs are divided into sections, called lobes. The right lung has three lobes, the left has two.
Cancer is the word used to describe a group of diseases in which normal cells change, grow and divide out of control. This out of control growth causes problems such as the creation of a mass (tumor). Cancer can also affect the tissue surrounding the mass and interfere with the functioning of organs. Cancer can also break away from the original mass and spread to other parts of the body (metastasis).
Lung cancer is when cells of the tissue of the lungs grow out of control.
A word about primary and secondary cancers: Other cancers can spread to the lungs. When this happens, it is not considered “lung cancer.” Primary lung cancer starts in the lung. Secondary lung cancer (or lung metastases) starts in another part of the body and spreads to the lungs. Secondary lung cancer is generally treated in the same way as the primary cancer, which may be different than primary lung cancer. The information on this page, and on this website, pertains only to primary lung cancer, that which starts in the lungs.