The following is provided by the National Cancer Institute

There are two major types of lung cancer: small cell and non-small cell – and different subtypes of non-small cell lung cancer.

Each type of lung cancer grows and spreads in different ways, and is treated differently. Non-small cell is the most common form of lung cancer, growing and spreading more slowly than the small cell type, which is also known as oat cell cancer, due to its appearance under a microscope. Small cell lung cancer is more likely to spread to other organs in the body.

According to the National Cancer Institute, cancer of the lung and bronchus (hereafter, lung cancer) is the second most common cancer among both men and women, second only to colorectal cancer.

Cigarette smoking accounts for nearly 90 percent of all lung cancers, and it is therefore the single most preventable cancer in existence. Quitting smoking is beneficial at all ages, and the earlier in life one quits, the greater the benefits. One study estimated that men who quit smoking by age 50 reduced their risk of lung cancer by almost two-thirds, compared to men who continued to smoke at age 75.

Other risk factors include:

Radon: A radioactive gas that you cannot see, smell or taste, radon forms in soil and rocks. People who work in mines may be exposed to radon. In some parts of the country, radon is found in houses. Radon damages lung cells, and people exposed to radon are at increased risk of lung cancer. The risk of lung cancer from radon is even higher for smokers.

Asbestos and other substances: People who have certain jobs (such as those who work in the construction and chemical industries) have an increased risk of lung cancer. Exposure to asbestos, arsenic, chromium, nickel, soot, tar and other substances can cause lung cancer. The risk is highest for those with years of exposure. The risk of lung cancer from these substances is even higher for smokers.

Air pollution: Air pollution may slightly increase the risk of lung cancer. The risk from air pollution is higher for smokers.

Family history of lung cancer: People with a father, mother, brother or sister who had lung cancer may be at slightly increased risk of the disease, even if they don't smoke.
Personal history of lung cancer: People who have had lung cancer are at increased risk of developing a second lung tumor.

Age over 65: Most people are older than 65 years when diagnosed with lung cancer.
Researchers have studied other possible risk factors. For example, having certain lung diseases (such as tuberculosis or bronchitis) for many years may increase the risk of lung cancer. It’s not yet clear whether having certain lung diseases is a risk factor for lung cancer.