Updated April 09, 2015.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Definition:
Non-small cell lung cancer is the most common form of lung cancer, accounting for 85 to 90% of all lung cancer cases. It tends to grow and spread more slowly than small cell lung cancer.

There are three types of cancer that are considered non-small cell lung cancer:

• Squamous cell carcinoma - starts in the middle of the lung close to an air tube (bronchus); approximately 25 to 30% of all non-small cell lung cancers are squamous cell.

• Adenocarcinoma - most often occurs in the outer part of the lung; 40% of non-small cell lung cancers fall under the adenocarcinoma category.

• Large-cell carcinoma - starts anywhere in the lungs and is often fast moving and harder to treat than the other two forms of non-small cell lung cancer; 10 to 15% of non-small cell lung cancers are large-cell lung cancer.

Another 10 to 15% of lung cancer cases are caused by small cell lung cancer.

Upward of 90% of all lung cancer cases in the United States today are directly attributable to cigarette smoking, with more people dying of lung cancer than any other form of cancer.

See also:

• All About Lung Cancer
• Smoking-Related Cancer Statistics