Lung cancer is the leading cause of cancer deaths in the United States and the world. There are two main types of lung cancer: non-small cell lung cancernon-small cell lung cancer (NSCLC), which comprises most cases of lung cancer, and small cell lung cancer (SCLC). Small cell lung cancer makes up about 13 percent of all lung cancer cases, according to the American Cancer Society (ACS). The disease occurs slightly more often in men than women. There is no significant difference in occurrence between races.

Lung cancer in general is the abnormal growth of malignant cells in the tissues of the lungs and airways. SCLC is an aggressive form of cancer that grows fast and spreads early in its development. Often it is not detected until it has metastasized (spread) to other areas of the body.

Symptoms of this form of lung cancer are the same as NSCLC and include persistent cough, blood in the sputum, breathing problems, chest pain and fatigue. To diagnose this cancer, a physician will take a medical history, perform a physical examination and order diagnostic tests such as chest x-rays, MRI, CAT scan and biopsy.

However, as with many cancers, symptoms may not appear until the disease has advanced. Because SCLC has often spread at the time of diagnosis, treatment is difficult, and SCLC has a lower survival rate as compared to NSCLC. An estimated 20 to 30 percent of people with extensive SCLC live at least one year, according to the ACS. This rate improves to 60 percent for people receiving treatment for limited-stage SCLC.

SCLC is usually treated with a combination of chemotherapy drugs and radiation therapy. Surgery is not usually recommended unless the disease remains limited to a small area of a lung. Although SCLC may be initially responsive to treatment, the disease often recurs.

Nearly all cases of small cell lung cancer are related to smoking, according to the ACS. There are no early detection methods, but quitting smoking and avoiding second-hand smoke reduce the likelihood of developing SCLC.