Lung Cancer: Forms of Lung Cancer

There are two major types of primary lung cancer:

Non-small Cell Lung Cancer (NSCLC) This is the most common type of lung cancer, accounting for about 85% of all cases.  It occurs when the epithelial cells that line the interior of the lungs become abnormal and grow out of control. These abnormal cells may then produce a solid mass, or tumor.   

NSCLC is divided into three categories:

  • Adenocarcinoma begins in the alveoli, the cells near the outer wall of the lungs that allow the exchange of oxygen and carbon dioxide.
  • Squamous cell carcinoma begins in the bronchial tubes, the air passages located in the center of the lungs.
  • Large cell carcinoma is a term for the 5% of all non-small cell lung cancers that do not clearly fall into the previous groups.

Small-cell lung cancer (SCLC) These tumors account for roughly 10 to 15 percent of all lung cancers.  Small cell lung cancers grow more rapidly and are more likely to spread to other organs. 

Two other cancers are found in the lungs:

Mesothelioma:  In Greek, meso means “middle,” and thelioma “lining.” This rare tumor affects the middle tissue in the lining of the lungs. It is often attributed to asbestos exposure, and represents 5 percent of all lung cancer cases. 

Thymoma: is a tumor of the thymus, an organ that is part of the lymphatic system, and is located in the chest behind the breastbone.  A thymoma can also affect the lining of the lungs.