The cancer cells may then be deposited in other organs of the body. A new colony of cancer cells which started in another organ is known as a metastasis. It is possible for cancer cells that begin in other organs to spread to the lungs. These cases are very different medical problems, however. These cancers are ordinary not treated by surgery or radiation therapy.
Smoking is the number one cause of lung cancer.
Cigarette smoke contains more than 4,000 different chemicals, many of which are proven carcinogens, while hundreds of others increase the cancer causing power of carcinogens. In a 1986 report, the Surgeon General of the U.S. concluded that involuntary smoking can cause lung cancer in nonsmokers. If you smoke, you are much more likely to develop the disease -men who smoke are estimated to be 22 times more likely to develop lung cancer, while women who smoke are estimated to be 12 times more likely. The more you smoke and the longer you smoke increases the risk. But if you stop smoking, the risk of cancer decreases steadily each year as abnormal cells are replaced by normal cells.