Small cell lung cancer begins when the cells surrounding the bronchi (the air tubes that lead from the trachea, or windpipe, to the lungs), called neuroendocrine cells, become abnormal and start to grow uncontrollably, forming a mass called a tumor.
Small cell lung cancer is less common than non-small cell lung cancer and accounts for about 13 percent of all lung cancer cases per year in the United States ― approximately 30,000. It develops in equal numbers among men and women.
Unlike non-small cell lung cancer, small cell lung cancer tends to spread quickly to other parts of the body and to the lymph nodes in the chest, which filter foreign particles out of the body. This means that when the cancer is found, it has often already begun to spread. For these and other reasons, diagnosis and treatment for small cell lung cancer is different from that of non-small cell lung cancer and usually involves chemotherapy.