Cancer Institute A national cancer institute
designated cancer center

What is Lung Cancer

Lung cancer is the leading cause of cancer death in both men and women. Lung cancer is a cancer that usually starts in the lining of the bronchi (the medium-sized airways within lungs), but can also begin in other areas of your respiratory system, including the trachea (main breathing tube), bronchioles (smaller branches of the air passages), or alveoli (the tissue farther out in the periphery of the lung).


Lung cancers are believed to develop over a period of many months to years. Nearly all lung cancers are “carcinomas”—tumors that begin in the lining or covering tissues of an organ. The tumor cells of each type of lung cancer grow and spread differently, and the treatments of these various types differ to some extent. About 85 percent to 90 percent of lung cancers belong to the group called non-small cell lung cancer.


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