Lung cancer is the uncontrolled growth of abnormal cells in the lung. Figure 01. There are two main types of lung cancer: non-small cell cancer and small cell cancer. Diagnosis, treatment and prognosis differ for small cell and non-small cell lung cancers.
Lung cancer causes more death than any other form of cancer in both men and women.
Smoking cigarettes is the number one cause of lung cancer. Of particular importance is the fact that teenage girls are the fastest growing group of smokers in the U.S. and that women seem to be more susceptible to the disease than men. Unfortunately, the number of cases of lung cancer is rapidly increasing in other parts of the world, as many people in third world countries are not aware of the dangers of smoking.
Cancer can grow in the lungs for many years before it is detected. Often people do not have symptoms until the disease has progressed, during which time the cancer grows undetected.
Each type of lung cancer varies depending on where it forms in the lungs.
Figure 01. Anatomy of the Lungs
Smoking tobacco products causes most cases of lung cancer. Approximately 90% of all lung cancers occur in people who either currently smoke, or who used to smoke. However, anyone, even nonsmokers, can get lung cancer.
Tobacco smoke contains many substances known to damage lung cells and promote tumor growth. Women seem to be more susceptible to these cancer-causing agents than men. Even nonsmoking women are more likely to get lung cancer than nonsmoking men.
Exposure to toxic chemicals can damage the lungs and give rise to some lung cancers. Certain chemicals are known to cause lung cancer. If you have been exposed to asbestos, uranium, arsenic, nickel, radon gas, chromium compounds, chloromethyl ether, vinyl chloride, coal products, or mustard gas, especially in a work setting, you should inform your doctor.
Air pollution is also thought to increase the risk of lung cancer.
Approximately 75% to 85% of lung cancers are non-small cell cancers. The non-small cell cancers are further divided into subgroups Table 01.
Table 1. Types of Non-small Cell Lung Cancer (Carcinoma)
Adenocarcinoma is the most common non-small cell cancer of the lung; it is often seen in nonsmokers and women. You probably will not have any symptoms when the cancer is found on a chest x-ray. Squamous cell carcinoma is the type of lung cancer that smokers tend to get. It sometimes located near or in a major airway, so the cancer can cause symptoms earlier in its growth. Coughing, producing bloody phlegm (sputum), shortness of breath, or pneumonia are common symptoms. It usually does not spread to distant sites in the body. It is more likely than other types of lung cancers to be cured with surgery. Large cell carcinomas represent about 10% of non-small cell cancers of the lung. It grows and spreads quickly, often spreading to other parts of the body including the brain. Large cell carcinoma does not have the specific features (such as cell shape or location of growth) of any of the other lung cancer cell types mentioned. Frequently it will turn out to be one of the subtypes if further tissue is obtained.
Small cell carcinomas are almost always found in patients who are smokers. They are the most aggressive types of lung cancers. Small cell cancer (sometimes called oat cell cancer) accounts for 15% to 25% of the lung cancer cases diagnosed annually. Symptoms don't usually develop until the cancer has progressed significantly.
Small cell cancers rapidly grow and spread (metastasize) to distant sites, and often have spread by time of discovery. Although both types of lung cancer are dangerous, prognosis for small cell cancer is usually worse than prognosis for non-small cell cancer.
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