- Small cell lung cancer (SCLC): cancer cells are small but quickly form large tumors that can progress to other parts of the body such as the lymph nodes, brain, liver, and bones. Also known as oat cell cancer, SCLC accounts for approximately 20% of all lung cell cancers.
- Non-small cell lung cancer (NSCLC): the most common form of lung cancer that incorporates a variety of cancer sub-types such as Squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. This type of cancer also spreads to other parts of the body but tends to progress slowly to different parts of the body slower than SCLC.
The principal cause of lung cancer is cigarette smoking. Before cigarette smoking became popular in the early 20th century, lung cancer was a rare occurrence. However, cases of lung cancer have exploded over the last century with an estimated 87% of lung cancer cases stemming from smoking.
Cigarette smoke contains over 4,000 different chemicals and many of these cancers have been proven to be carcinogens (cancer-causing substances). The probability of lung cancer increases with the amount of time and quantity an individual smokes.
Additionally, the use of smokeless tobacco products and the smoking of other forms of tobacco products are major causes of lung cancer.
Another major cause of lung cancer is second-hand smoke, which is a byproduct of smoking. Chemicals present in tobacco smoke affect nonsmokers who are inhaling the smoke, and second hand smoke has been identified as causing approximately 3,000 lung cancer deaths per year. Second hand smoke has also been identified as causing approximately 50,000 deaths from heart disease per year.
The second biggest cause of lung cancer is exposure to radon: an invisible, odorless, and radioactive gas. Radon gas is commonly found in mines as well as in the home. It often emerges from soil underneath a building that enters through gaps and cracks in a building’s foundation or insulation. Radon can also enter a home through other openings such as pipes, drains, and walls. Currently, it is estimated that radon exposure makes up 12% of all lung cancer deaths, causing between 15,000 and 22,000 lung cancer deaths per year.
An additional cause of lung cancer is on-the-job exposure to carcinogens. The most common carcinogen is asbestos, (a substance commonly used in shipbuilding, insulation work, and brake repair) which if inhaled can cause cell damage that increases the potential of lung cancer. Additional carcinogens that are often found on work sites include: uranium, arsenic, and certain petroleum products.