Introduction

This content has been reviewed and approved by

Chandra P. Belani, MD
Deputy Director, Penn State Cancer Institute
Miriam Beckner Professor of Medicine
Penn State University School of Medicine

Lung cancer is the second most frequently diagnosed cancer in both men and women in the United States. In 2010, about 15 percent of all new cancer cases in men and 14 percent in women will be diagnosed as lung cancer, according to the American Cancer Society. Small cell lung cancer is one of the two most common types of lung cancer, accounting for 13 percent of new cases, according to the ACS.

Cancer of the lung occurs as cells reproduce without stopping and gain the ability to spread. It usually starts in the bronchi (the main airways of the lungs), but can also begin in the trachea (the windpipe, which leads from the throat to the lungs) or in the smaller airways of the lungs. Nearly all lung cancers are carcinomas, developing from abnormal cells in the lining or covering tissue of an organ.

Small cell lung cancer may also be called oat cell cancer because the cancer cells have a characteristic appearance under the microscope, looking like oats. Other names for lung cancer include pulmonary carcinoma, bronchial carcinoma, and bronchoalveolar cell carcinoma. "Pulmonary" means "related to the lung," and comes from the Latin word for lung (pulmo). "Bronchoalveolar" describes the small lung structures that branch out from the bronchi.

The leading cause of lung cancer is tobacco smoking. Smoking causes more than 90 percent of all lung cancers. However, not all people who smoke develop lung cancer, and not all cases of lung cancer are caused by smoking. Other risk factors for lung cancer include breathing secondary smoke (smoke from other people's tobacco use), smoking marijuana, and exposure to asbestos or other harmful agents, such as radioactive substances, arsenic, vinyl chloride, mustard gas, radon gas, or diesel exhaust.