Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. It usually grows and spreads more slowly than small cell lung cancer.

There are three forms of NSCLC:

• Adenocarcinomas are often found in an outer area of the lung.
• Squamous cell carcinomas are usually found in the center of the lung by an air tube (bronchus).
• Large cell carcinomas can occur in any part of the lung. They tend to grow and spread faster than the other two types.

Smoking causes most cases of lung cancer. The risk depends upon the number of cigarettes smoked every day and for how long someone has smoked. Being around the smoke from others (secondhand smoke) also raises your risk for lung cancer. However, people who do not smoke and have never smoked have become sick with lung cancer.

A review of decades of research has recently shown that smoking marijuana may help cancer cells grow, but there is no direct link between the drug and developing lung cancer.

High levels of air pollution and drinking water containing high levels of arsenic can increase your risk for lung cancer. Radiation therapy to the lungs can also increase the risk.

Working with or near the following cancer-causing chemicals or materials can also increase your risk:

• Asbestos
• Products using chloride and formaldehyde
• Certain alloys, paints, pigments, and preservatives