Lung Cancer Overview

What Is It?

One of the most common cancers, lung cancer usually occurs when a cancer-causing agent, or carcinogen, triggers the growth of abnormal cells in the lung. These cells multiply out of control and eventually form a tumor. As the tumor grows, it destroys nearby areas of the lung. Eventually, tumor cells can spread (metastasize) to nearby lymph nodes and other parts of the body. These include the

  • liver

  • bones

  • adrenal glands

  • brain.

In most cases, the carcinogens that trigger lung cancer are chemicals found in cigarette smoke. However, more and more lung cancers are being diagnosed in people who have never smoked.

Lung cancers are divided into two groups, based on how their cells look under the microscope: non-small cell lung cancer and small cell lung cancer. Non-small cell lung cancer may be localized. This means that it is limited to the lung or that it hasn't spread beyond the chest. As a result, it can usually be treated with surgery. Small cell lung cancer is rarely localized, even when it is detected early. It is rarely treated with surgery. Knowing whether the cancer has spread is critical, because it affects treatment decisions.

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