What Is Lung Cancer?

Lung cancer is cancer that begins in the lungs. It is the second most common cancer in both men and women, as well as the leading cause of cancer death in both men and women.  

There are two main types of lung cancer. They are non-small cell lung cancer and small cell lung cancer. A doctor called a pathologist uses a microscope to look at the cancer cells collected during your biopsy to tell which type of cancer you have. These two types of lung cancer grow and spread in different ways. Therefore, they are treated differently. Non-small cell lung cancer usually grows and spreads more slowly than small cell lung cancer.  

Non-small cell lung cancer (NSCLC)

About 85% to 90% of lung cancers are non-small cell. There are three main types of NSCLC. While there are slight differences between them, they tend to have a similar prognosis (outlook) and are generally treated the same way:

• Adenocarcinoma. This is the most common kind of non-small cell lung cancer. And it's the most common type of lung cancer in nonsmokers. It tends to grow in the outer edges of your lungs, and usually grows more slowly than other types of lung cancer. 
• Squamous cell carcinoma (epidermoid carcinoma). This type of non-small cell lung cancer develops more often in smokers. These cancers tend to start in the middle part of the lungs.
• Large cell. This is the least common of the three kinds of non-small cell lung cancer. It tends to grow and spread early to other organs, which can make it harder to treat.

Small cell lung cancer (SCLC)

Only about 10% to 15% of people diagnosed with lung cancer have small cell lung cancer. Small cell lung cancer is also called oat cell cancer. It grows and spreads more quickly than non-small cell lung cancer. It often spreads to other parts of the body at an early stage. This type of cancer is almost always associated with smokers. If you don't smoke, you aren't likely to get small cell lung cancer.