American Medical Association Family Medical Guide - American Medical Association [394]
Normal cells in the lungs can also become cancerous when they are exposed to carcinogens other than those in tobacco smoke, such as coal tar and radon (a radioactive gas that can seep into houses from the ground). Exposure to asbestos (an insulating building material) can cause cancer of the pleural membranes that surround the lungs. The risk of developing lung cancer is related to the amount of exposure to the cancer-causing substance. Some carcinogens react together to significantly increase the risk of lung cancer. For example, if you smoke cigarettes and are exposed to asbestos or radon, your risk of lung cancer multiplies. In rare cases, cancer cells from other parts of the body (usually the breasts, bones, thyroid gland, or kidneys) may be carried through the bloodstream or lymphatic system to the lungs, where they form tumors composed of the same type of cancerous cells as that of the original tumor.
Lung cancer that begins in the lungs is classified as one of two types: small cell (also called oat cell) and non-small cell. Non-small cell lung cancer accounts for 80 percent of all cases of lung cancer but usually spreads to distant organs more slowly than small cell lung cancer. Small cell lung cancer is more likely to spread throughout the body quickly, but it is also more likely than non-small cell lung cancer to respond to chemotherapy (see page 23).
Symptoms
An early symptom of lung cancer is a persistent cough, which usually produces bloodstained phlegm. You also may be breathless, wheeze when you breathe, and have chest pains. The chest pains may be dull and persistent, or sharp, intensifying when you take a deep breath.
If lung cancer spreads
If lung cancer goes undetected, it can spread (metastasize) from the lungs to other areas of the body. The areas to which lung cancer is most likely to spread include the lymph nodes, brain, bones, liver, and adrenal glands. The symptoms of cancer in these sites vary depending on the organs that are affected. For example, a tumor in the brain can cause paralysis.
However, most cancerous tumors in the lungs begin to grow without causing symptoms. Often, people who have lung cancer do not develop symptoms until the cancer is at an advanced stage. It can take 10 to 12 years for a cancerous cell to grow into a tumor that is large enough to cause symptoms or be detected on an X-ray. Sometimes the lung cancer is not detected until it has spread to another organ where it causes symptoms. For this reason, the majority of cancerous tumors in the lungs are diagnosed at a late stage, usually too late for a cure. Only 7 percent of all people with lung cancer are cured. If a person with lung cancer cannot be cured with surgery at the time the cancer is found, death will occur in less than a year in 50 percent of cases.
Diagnosis
If you are having symptoms of lung cancer, your doctor will listen to your chest with a stethoscope and order a chest X-ray. If your doctor suspects you have lung cancer or if the X-ray shows signs of a possible tumor, he or she will probably recommend more diagnostic tests such as a CT scan (see page 112). He or she will also examine phlegm or tissue samples from your lungs to see if they contain cancerous cells. These biopsy samples are obtained by bronchoscopy (see page 661), needle aspiration (in which tissue samples are removed from the lungs using a needle and syringe), or surgery.