What is lung cancer?

There are 2 major forms of lung cancer: non-small cell and small cell. Non-small cell lung cancer is more common than small cell lung cancer, and it generally grows and spreads more slowly. Small cell lung cancer is almost always caused by smoking. In fact, cigarette smoking is the single most important risk factor for developing lung cancer. If you smoke, talk to your doctor about quitting. He or she can help you figure out how to kick the habit.