Cancer
Overview See All Anatomy of the Respiratory System in Overview A detailed look at the respiratory system and how it works....more Smoking and Respiratory Diseases in Overview Diseases caused by smoking kill more than 480,000 people in the U.S. each year. Here's a look at the risks linked to smoking, as well as information to help you quit. ...more Lung Cancer: Symptoms in Overview Lung cancer often doesn't cause symptoms in its early stages. In fact, many lung cancers don't cause symptoms until they have already spread.