Table of Contents
- Lung cancer facts
- What is lung cancer?
- How common is lung cancer?
- What are the causes and risk factors for lung cancer?
- What causes lung cancer? (Part 2)
- What causes lung cancer? (Part 3)
- What are the types of lung cancer?
- What are lung cancer symptoms and signs?
- What specialists treat lung cancer?
- How do health-care professionals diagnose lung cancer?
- How do health-care professionals diagnose lung cancer? (Continued)
- How do health-care professionals determine lung cancer staging?
- What is the treatment for lung cancer?
- What is the treatment for lung cancer? (Part 2)
- What is the treatment for lung cancer? (Part 3)
- What is the prognosis and life expectancy of lung cancer?
- Is it possible to prevent lung cancer?
What are the types of lung cancer?
Lung cancers, also known as bronchogenic carcinomas because they arise from the bronchi within the lungs, are broadly classified into two types: small cell lung cancers (SCLC) and non-small cell lung cancers (NSCLC). This classification is based upon the microscopic appearance of the tumor cells themselves, specifically the size of the cells. These two types of cancers grow and spread in different ways and may have different treatment options, so a distinction between these two types is important.
SCLC comprise about 20% of lung cancers and are the most aggressive and rapidly growing of all lung cancers. SCLC are strongly related to cigarette smoking, with only 1% of these tumors occurring in nonsmokers. SCLC metastasize rapidly to many sites within the body and are most often discovered after they have spread extensively. Referring to a specific cell appearance often seen when examining samples of SCLC under the microscope, these cancers are sometimes called oat cell carcinomas.
NSCLC are the most common lung cancers, accounting for about 80% of all lung cancers. NSCLC can be divided into several main types that are named based upon the type of cells found in the tumor:
- Adenocarcinomas are the most commonly seen type of NSCLC in the U.S. and comprise up to 50% of NSCLC. While adenocarcinomas are associated with smoking like other lung cancers, this type is observed as well in nonsmokers who develop lung cancer. Most adenocarcinomas arise in the outer, or peripheral, areas of the lungs.
- Bronchioloalveolar carcinoma is a subtype of adenocarcinoma that frequently develops at multiple sites in the lungs and spreads along the preexisting alveolar walls.
- Squamous cell carcinomas were formerly more common than adenocarcinomas; at present, they account for about 30% of NSCLC. Also known as epidermoid carcinomas, squamous cell cancers arise most frequently in the central chest area in the bronchi.
- Large cell carcinomas, sometimes referred to as undifferentiated carcinomas, are the least common type of NSCLC.
- Mixtures of different types of NSCLC also are seen.
Other types of cancers can arise in the lung; these types are much less common than NSCLC and SCLC and together comprise only 5%-10% of lung cancers:
- Bronchial carcinoids account for up to 5% of lung cancers. These tumors are sometimes referred to as lung neuroendocrine tumors. They are generally small (3 cm-4 cm or less) when diagnosed and occur most commonly in people under 40 years of age. Unrelated to cigarette smoking, carcinoid tumors can metastasize, and a small proportion of these tumors secrete hormone-like substances that may cause specific symptoms related to the hormone being produced. Carcinoids generally grow and spread more slowly than bronchogenic cancers, and many are detected early enough to be amenable to surgical resection.
- Cancers of supporting lung tissue such as smooth muscle, blood vessels, or cells involved in the immune response can rarely occur in the lung.
As discussed previously, metastatic cancers from other primary tumors in the body are often found in the lung. Tumors from anywhere in the body may spread to the lungs either through the bloodstream, through the lymphatic system, or directly from nearby organs. Metastatic tumors are most often multiple, scattered throughout the lung, and concentrated in the peripheral rather than central areas of the lung.