Thoracic Oncology Program: Lung

Types of Lung Cancer

There are several types of lung cancer, but most fall into three main categories: small-cell lung cancer, non-small cell lung cancer and malignant mesothelioma. These three types of lung cancer act differently and are treated differently.

Non-Small Cell Lung Cancer (NSCLC; 85-90% of all lung cancers)

Non-small cell lung cancer (NSCLC) is the most common form of lung cancer, comprising 80-85% of all lung cancers.

It is divided into four major subtypes:


  • Represents up to 60% of the non-small cell lung cancer cases in the United States
  • Is the most common lung cancer among women
  • Usually starts on the outer edges of the lungs
  • May spread to other parts of the body
  • Is the type that occurs in non-smokers as well as smokers

Squamous cell carcinoma

  • Represents about 30% of NSCLC lung cancers in the United States
  • Usually starts centrally in one of the bronchi
  • Frequently spreads to regional lymph nodes but tumors are slow growing
  • Is strongly associated with smoking

Large cell undifferentiated carcinoma

  • Represents about 10% of NSCLC lung cancers in the United States
  • May occur in any part of the lung
  • Frequently a diagnosis of exclusion
  • Is strongly associated with smoking

Bronchoalveolar carcinoma

  • Is a rare sub-type of adenocarcinoma and represents only 3% of all lung cancers
  • Typically presents in younger patients, women and non-smokers
  • Initially spreads through tiny sacs in the lungs called alveoli rather than in solid tumors

Small Cell Lung Cancer (SCLC; 10-15% of all lung cancers)

Small-Cell Lung Cancer (SCLC) typically grows more rapidly than NSCLC. SCLC spreads to the lymph nodes and other organs more quickly than NSCLC and is seen predominantly in smokers or former smokers (about 98% of cases are attributed to smoking). SCLC usually starts in one of the large bronchi. At the time of diagnosis, it usually has spread and is considered a systemic disease. SCLC is more responsive to a variety of chemotherapy drugs than NSCLC. It was previously called “oat cell” cancer because the cells are small and oval like oat grains.


Mesothelioma is a rare type of cancer often beginning in the outer lining of cells that surround the lungs. It occurs most often many years after prolonged exposure to asbestos. Family members can develop mesothelioma by secondary exposure through inhalation, i.e. doing the laundry of an asbestos worker. Smoking and asbestos exposure together greatly increase the risk of developing mesothelioma.

For more information on mesothelioma, click here.