This website is for informational use only and does not provide any medical advice.

What is lung cancer?

Lung cancer is cancer that usually starts in the lining of the bronchi (the main airways of the lungs), but can also begin in other areas of the respiratory system, including the trachea, bronchioles or alveoli.

There are two main types:

  • Non-small cell lung cancer (NSCLC) is the most common type and makes up about 85 percent of all cases. It usually grows and spreads more slowly than the small cell type. Smoking causes most cases, but NSCLC risks increase due to exposure to secondhand smoke and substances such as asbestos, radon, certain chemicals and products using chloride and formaldehyde.
  • Small cell lung cancer (SCLC) is a fast-growing type. It spreads much more quickly than the non-small cell type. Almost all cases of SCLC are due to cigarette smoking.

Mesothelioma, an otherwise rare cancer of the chest lining, is caused by asbestos exposure. The American Lung Association estimates that 2,000 to 3,000 individuals are diagnosed with mesothelioma each year in the U.S.


Lung cancer is normally discovered in patients experiencing specific symptoms such as:

  • Persistent cough — the most common symptom
  • Shortness of breath or wheezing
  • Recurring lung infections such as pneumonia or bronchitis

Be aware that these symptoms could be due to conditions other than cancer, so it’s best to see a doctor right away.

The first step to a diagnosis is usually a physical. A doctor will also consider medical history, risk factors and any related medical or precancerous conditions.

If a doctor suspects that someone might have cancer, the patient will be sent for testing.

A number of procedures and tests are used to deliver an accurate diagnosis as well as to determine how far the cancer has spread, known as the stage of the cancer:

  • Chest X-ray — This test can identify any large mass or spot on the lungs.
  • Lung cancer screening uses a combination of X-rays and low-dose computerized tomography (CT) or CAT (computerized axial tomography) scans with reduced radiation to identify lung nodules. These scans are more likely than routine chest X-rays to show lung tumors.
  • CT or CAT (computerized axial tomography) scan — More detailed than an X-ray, this procedure uses a combination of X-rays and computer technology to produce detailed cross-sectional images.
  • MRI (magnetic resonance imaging) — A powerful magnet, radio waves and computer imaging combine to create a series of highly detailed pictures of areas inside the body.
  • PET (positron emission tomography) scan — This scan uses a small amount of radioactive sugar to highlight the presence and stage of the cancer.
  • Bronchoscopy — A thin viewing instrument (bronchoscope) looks at the airways in the lungs or the bronchi.
  • Endobrachial ultrasound (EBUS) — A small camera and sound waves show the airway and structures through the airway walls. Tissue can be extracted for biopsy, cancer staging and treatment planning.
  • Biopsy — A piece of tissue is extracted from a node or tumor to determine the type, stage and genetic signature of the tumor.
  • Mediastinoscopy — This surgical procedure examines with biopsies of the organs and tissues between the lungs and nearby areas for abnormalities.
  • Bone scan — This procedure uses a small dose of radioactive substance to determine if the cancer has spread to the bone.

Once a diagnosis has been confirmed, a doctor will conduct one or more of the diagnostic imaging tests listed above to determine the location of the cancer and how far it has spread. Staging is necessary in order to design the most effective treatment plan.

Non-small cell cancer is divided into several stages:

  • Occult — Cancer cannot be seen by imaging or bronchoscopy.
  • Stage 0 — The earliest stage in which cancer can be detected (also known as carcinoma in situ).
  • Stage I — Cancer is confined to the lung.
  • Stage II — Cancer is either large or has spread to nearby lymph nodes.
  • Stage IIIA — Cancer has spread to certain lymph nodes on the same side of the chest as the primary tumor.
  • Stage IIIB — A tumor of any size that has spread to distant lymph nodes, has invaded other structures in the chest (such as the heart or esophagus), or has a malignant pleural effusion (fluid build-up containing cancer cells between the layers lining the lungs).
  • Stage IV — Cancer has spread to other parts of the body.

Small cell cancer is divided into two stages:

  • Limited — Cancer is in the lung where it started and may have spread to the area between the lungs or to the lymph nodes above the collarbone.
  • Extensive — Cancer has spread beyond the lung or the area between the lungs or the lymph nodes above the collarbone to other places in the body.