Lung cancer affects more than 200,000 Americans each year. Although cigarette smoking is the main cause, anyone can develop lung cancer.
The lungs absorb oxygen from the air and bring the oxygen into the bloodstream, which delivers it 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 then carbon dioxide leaves the body when people exhale.
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.
Lung cancer begins when cells in the lung grow out of control and form a mass (also called a tumor, lesion or nodule). A cancerous tumor is a collection of a large number of cancer cells and appears as a mass within the lung tissues. A lung tumor can begin anywhere in the lung.
Once a cancerous lung tumor begins to grow, it may or may not shed cancer cells. Shed 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, which drain into collecting stations called lymph nodes. Lymph nodes are located in the lungs, in 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 leaves its site of origin and moves into a lymph node or to a far away part of the body through the bloodstream, it is called metastasis.
There are two major types of lung cancer: non-small cell and small cell. Non-small cell lung cancer (NSCLC) arises from epithelial cells and is the most common type. Small cell lung cancer begins in the nerve cells or hormone-producing cells. 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 non-small cell from small cell lung cancer because the two types of cancer are usually treated in different ways.
The location and size of the initial lung tumor and whether it has spread to lymph nodes or more distant sites determines the stage of lung cancer. The type of lung cancer and stage of the disease determine what type of treatment is needed.