Definition of Lung cancer:

Lung cancer is cancer that begins in the lungs, the two organs found in the chest that help you breathe.

The lungs are made up of areas called lobes. The right lung has three lobes; the left lung has two, so there's room for the heart. When you breathe, air goes through your nose, down your windpipe (trachea), and into the lungs where it spreads through tubes called bronchi. Most lung cancer begins in the cells that line these tubes.

There are two main types of lung cancer:

• Non-small cell lung cancer (NSCLC) is the most common type of lung cancer.
• Small cell lung cancer makes up about 20% of all lung cancer cases.

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

If the cancer started somewhere else in the body and spread to the lungs, it is called metastatic cancer to the lung.

Causes, incidence, and risk factors:

Lung cancer is the deadliest type of cancer for both men and women. Each year, more people die of lung cancer than breast, colon, and prostate cancers combined.

Lung cancer is more common in older adults. It is rare in people under age 45.

Cigarette smoking is the leading cause of lung cancer.

The more cigarettes you smoke per day and the earlier you started smoking, the greater your risk of lung cancer. There is no evidence that smoking low-tar cigarettes lowers the risk.

However, lung cancer has occurred in people who have never smoked.

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
• 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