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 can block or narrow airways and make breathing difficult. 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.