Oncologist-approved cancer information from the American Society of Clinical Oncology
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Lung Cancer

This section has been reviewed and approved by the Cancer.Net Editorial Board, 6/2013
Overview

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ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to Lung Cancer. To see other pages, use the colored boxes on the right side of your screen. Think of those boxes as a roadmap to this full guide. Or, click “Next” at the bottom of each page.

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 make 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 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 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 first. 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 the Stages section) determine what type of treatment is needed.

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