Lung cancer is the leading cause of cancer deaths in men and women throughout the world. Lung cancer is often thought of as a single disease, but it is commonly divided into two main types: non-small cell lung cancers (NSCLC) and small cell lung cancer (SCLC). Small cell lung cancer is less common than NSCLC, accounting for only about 13 percent of lung cancer cases. SCLC is also called oat cell carcinoma, because it appears like oat grains under a microscope.

Lung cancer is the abnormal growth of malignant cells in the tissues of the lungs or airways. Cancer cells develop because of damage that occurs to DNA, the genetic blueprint present in every cell. DNA governs how a cell grows, divides and dies. The body can usually repair damage to DNA. In cancer cells, however, the DNA is not repaired and the abnormal cells reproduce very quickly and often live longer than normal cells.

The lungs are sponge-like, cone-shaped organs located in the chest cavity. The left lung has three lobes and the right has two lobes. The lungs are part of the respiratory system and are responsible for the healthy exchange of gases that nourish and cleanse the body’s cells. There is a system of small (bronchioles) and larger tubes (bronchi) that carry air to and from the lungs for processing in tiny air sacs called alveoli. The oxygen is carried through the bloodstream and made available to the cells in the body. The bloodstream also picks up the waste product carbon dioxide from the cells, and transports it to the lungs to exhale.

Lung cancers can spread quickly, but SCLC is particularly aggressive. The disease is characterized by rapid division of cells (mitosis) and a high growth factor. SCLC usually begins in the bronchi, though a small percentage may begin in a peripheral area of the lung, such as the lining. It often metastasizes by way of the lymphatic system and blood vessels at an early stage.

Because it can spread so quickly, SCLC is not staged using traditional methods. Physicians use two categories to stage SCLC, according to the National Cancer Institute (NCI):

• Limited-stage SCLC. The cancer is found in one lung, the tissues between the lungs and nearby lymph nodes only. About 30 percent of patients with SCLC will be in the limited stage, according to the NCI, with a median survival rate of 16 to 24 months. However, surgery may be possible in certain patients, which can improve the prognosis.
  
  
• Extensive-stage SCLC. The cancer has spread outside of the lung in which it began or to distant parts of the body. The median prognosis for extensive stage is 6 to 12 months.

SCLC can be fatal within two to four months from the time of diagnosis because it typically has spread by the time it is detected. However, SCLC is more responsive initially to chemotherapy and radiation therapy as compared to other forms of lung cancer. An estimated 20 to 30 percent of people with extensive SCLC live at least one year, and this rate improves to 60 percent for people receiving treatment for limited stage SCLC.

Small cell lung cancer occurs slightly more often in men than women. There is no significant difference in occurrence between black people and white people. However, an estimated 98 percent or more of SCLC patients have a history of smoking, according to the American Cancer Society (ACS). Before the 20^th century, when cigarettes were not mass produced or readily available, lung cancer in general was rarely seen. As cigarettes became widely available, cases of lung cancer rose dramatically.

The connection between cigarettes and lung cancer is overwhelming. Wherever smoking is on the increase in the world, there is a corresponding rise in lung cancer cases. Other risk factors for lung cancers include family history of lung cancer, age and exposure to certain environmental agents such as radon gas or asbestos.

The ACS estimates there will be more than 213,000 new cases of lung cancer (both NSCLC and SCLC) in 2007. The disease will be responsible for about 161,000 American deaths in the same year. The most effective means to prevent lung cancer is not smoking or quitting the habit.