Lung cancer is cancer that begins in the lungs, the organs in your chest that help you breathe. Each year, more people die of lung cancer than breast, colon, and prostate cancers combined, making lung cancer the deadliest type of cancer for both women and men. It's more common in older adults, and is rare in people under the age of 45.

Your lungs are made up of two sponge-like lobes. The right lung has three lobes; the left lung has two. When you breathe, air travels through your nose, down your windpipe (trachea), and into your lungs, where it spreads through tubes called bronchi. Most lung cancer begins in the cells that line these tubes.

Two Main Types of Lung Cancer:

  • Non-small cell lung cancer (NSCLC)—the most common form
  • Small cell lung cancer (SCLC)—about 20 percent of all lung cancer cases

If the lung cancer is made up of both types, it's called mixed small cell/large cell cancer.

Non-small cell lung cancer generally grows and spreads more slowly than small cell lung cancer. There are three common forms, but while the cells of each are different in size, shape, and chemical makeup, they are grouped together because the prognosis (predicted outcome) and approach to treatment are very similar. They include the following:

Adenocarcinomas:

  • Often found in an outer area of the lung
  • Comprise about 40 percent of all lung cancers
  • Start in cells that normally secrete substances like mucus
  • Most common type of lung cancer for non-smokers and smokers alike
  • More common in women than men
  • Lung cancer most likely to affect younger people
  • Slow growing form of cancer; more likely to be detected before spreading outside of the lungs

Squamous cell carcinomas:

  • Usually found in the center of the lung next to an air tube
  • Comprise about 25-30 percent of all lung cancers
  • Begin in squamous cells (flat cells that line the inside of your airways)
  • Linked to a history of smoking.

Large cell carcinomas:

  • Can occur in any part of the lung
  • Grow and spread faster than the other two types, making it more difficult to treat
  • Account for about 10 to 15 percent of lung cancers

Small cell lung cancer often starts in the bronchi near the center of the chest, and tends to spread rapidly, usually before it causes symptoms. There are two types of small lung cancer: small cell carcinoma and combined small cell carcinoma. The cancer cells can multiply quickly and spread to the bones, brain, lymph nodes, adrenal glands, and liver. Sometimes the affected areas appear as tumors on x-rays and other imaging tests, but early on, these cancers may be difficult to detect. It is very rare for someone who has never smoked to have small cell lung cancer.

Symptoms
As symptoms of lung cancer can mimic those of other illnesses, it's important to see your doctor if any of these persist:

  • A cough or chest pain that doesn't go away
  • Shortness of breath
  • Wheezing
  • Coughing up blood
  • Hoarseness
  • Swelling of the face and neck
  • Loss of appetite
  • Weight loss for no known reason
  • Unusual tiredness

Contributing Factors
Secondhand smoke (breathing the smoke of others) increases your risk of lung cancer. According to the American Cancer Society, an estimated 3,000 non-smoking adults will die each year from lung cancer related to breathing secondhand smoke.

The following may also increase one's risk of lung cancer:

  • High levels of air pollution
  • High levels of arsenic in drinking water
  • Radon gas
  • Asbestos
  • A family history of lung cancer
  • Radiation therapy to the lungs
  • Exposure to cancer-causing chemicals such as uranium, beryllium, vinyl chloride, nickel chromates, coal products, mustard gas, chloromethyl ethers, gasoline, and diesel exhaust

Treatment
Treatment depends on the type and the stage of the cancer, the patient's general health, and whether there are other contributing factors.

Non-small cell lung cancer: Surgery is the often the option of choice if the cancer has not spread beyond nearby lymph nodes. The surgeon may remove:

  • One of the lobes of the lung (lobectomy)
  • Only a small part of the lung (wedge or segment removal)
  • The entire lung (pneumonectomy)

Some patients need chemotherapy. Chemotherapy uses drugs to kill cancer cells and stop new ones from growing.

  • Chemotherapy alone is often used when the cancer is advanced (Stage IV).
  • It may also be given before surgery or radiation to make those treatments more effective.
  • It may be given after surgery to kill any remaining cancer.

Small cell lung cancer: Since small cell lung cancer spreads quickly, removing the tumor rarely cures the cancer. Chemotherapy, which can reach cancer cells throughout the body, is the main treatment for small cell lung cancers.

Sources:

David H. Johnson, William J. Blot, David P. Corbone, et al. "Cancer of the Lung: Non-Small Cell Lung Cancer and Small Cell Lung Cancer." In Martin D. Abeloff, James O. Armitage, John E. Niederhuber, et al., eds. Abeloff's Clinical Oncology, 4th ed; courtesy of Mercy's McGlannan Health Sciences Library.

National Cancer Institute. "Lung Cancer." http://www.cancer.gov/cancertopics/types/lung.

American Cancer Society. "Lung Cancer." http://www.cancer.org/cancer/lungcancer/index.