Lung cancer affects more than 200,000 Americans each year. Although cigarette smoking is the main cause, anyone can develop lung cancer. Lung cancer is always treatable, no matter the size, location, whether the cancer has spread, and how far it has spread.

About the lungs

When a person inhales, the lungs absorb oxygen from the air and bring the oxygen into the bloodstream for delivery to the rest of the body. As the body's cells use oxygen, they release carbon dioxide. The bloodstream carries carbon dioxide back to the lungs, and the carbon dioxide leaves the body when a person exhales. The lungs contain many different types of cells. Most cells in the lung are epithelial cells. Epithelial cells line the airways and produce mucus, which lubricates and protects the lung. The lung also contains nerve cells, hormone-producing cells, blood cells, and structural or supporting cells.

About lung cancer

There are two major types of lung cancer: non-small cell and small cell. Non-small cell lung cancer (NSCLC) comes from epithelial cells and is the most common type. Small cell lung cancer begins in the nerve cells or hormone-producing cells of the lung. The term “small cell” refers to the size and shape of the cancer cells as seen under a microscope. It is important for doctors to distinguish NSCLC from small cell lung cancer because the two types of cancer are usually treated in different ways.

Lung cancer begins when cells in the lung change and grow uncontrollably to form a mass called a tumor (or a lesion or nodule). A tumor can be benign (noncancerous) or malignant (cancerous). A cancerous tumor is a collection of a large number of cancer cells that have the ability to spread to other parts of the body in a process. A lung tumor can begin anywhere in the lung.

Once a cancerous lung tumor grows, it may or may not shed cancer cells. These cells can be carried away in blood or float away in the natural fluid, called lymph, that surrounds lung tissue. Lymph flows through tubes called lymphatic vessels that drain into collecting stations called lymph nodes, the tiny, bean-shaped organs that help fight infection. Lymph nodes are located in the lungs, the center of the chest, and elsewhere in the body. The natural flow of lymph out of the lungs is toward the center of the chest, which explains why lung cancer often spreads there. When a cancer cell moves into a lymph node or to a distant part of the body through the bloodstream, it is called metastasis.

The stage of lung cancer is determined by the location and size of the initial lung tumor and whether it has spread to lymph nodes or more distant parts of the body. The type of lung cancer (NSCLC versus small cell) and stage of the disease (discussed later in Staging) determine what type of treatment is needed.

Find out more about basic cancer terms used in this section.

Looking for More of an Overview?

If you would like additional introductory information, explore these related items on Cancer.Net:

• ASCO Answers Fact Sheet: Read a one-page fact sheet (available in PDF) that offers an easy-to-print introduction for this type of cancer.

• Cancer.Net En Español: Read about lung cancer in Spanish. Infórmase sobre cáncer de pulmón en español.

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