Lung cancer is classified by the type of cells within the tumor. Each type of lung cancer grows and is treated in a different way. Lung cancers are divided into two main groups.
Non-Small Cell Lung Cancer (NSCLC)
This is the most common type of lung cancer. The categories of non-small cell lung cancer are named for the type of cells in the cancer:
- Adenocarcinoma begins in cells that line the alveoli and make mucus. It is found more often in nonsmokers, women and younger people.
- Squamous cell carcinoma (cancer) begins in thin, flat cells in the lungs, and tobacco smoking most often causes it. It also is called epidermoid carcinoma.
- Large cell carcinoma (cancer) begins in certain types of large cells in the lungs.
Small Cell Lung Cancer
Also known as oat-cell cancer, this type of lung cancer makes up less than 20% of lung cancers and almost always is caused by tobacco smoking. It often starts in the bronchi, then quickly grows and spreads to other parts of the body, including the lymph nodes.
Less common types of lung cancer include:
- Carcinoid tumors
- Salivary gland carcinoma
- Some sarcomas
- Cancer of unknown primary
Cancer found in the lungs is sometimes another type of cancer that started somewhere else in the body and spread, or metastasized, to the lungs. These tumors are called lung metastases, and they are not the same as lung cancer. They usually are the primary, or original, type of cancer.