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Lung cancer
is uncontrolled cell growth in the lungs. This uncontrolled growth may lead to metastasis, which is the invasion of adjacent tissue beyond the lungs. Lung cancer is the most common cause of cancer-related deaths in men and women, and is responsible for 1.3 million deaths annually worldwide. Lung cancers can develop in any part of the lung, but 90%-95% of cancers of the lung are thought to arise from the epithelial cells. These are the cells lining the larger and smaller airways (bronchi and bronchioles); for this reason, lung cancers are sometimes called bronchogenic cancers or bronchogenic carcinomas. Lung cancers also can arise from the pleura (called mesotheliomas) or rarely from supporting tissues within the lungs, for example, the blood vessels.
The main types of lung cancer are small cell lung carcinoma and non-small cell lung carcinoma. The distinction is important because the treatment for the disease varies, depending on the type. This classification of the two types of lung cancer is based on the microscopic appearance of the tumor cells themselves. Small cell lung carcinoma makes up about 20% of lung cancers and is the most aggressive and rapidly growing of all lung cancers. It is strongly related to cigarette smoking. Cigarette smoke contains over 60 known carcinogens. This type often metastasize rapidly to other sites within the body and are most often discovered after they have already spread extensively. The second type of lung cancer, non-small cell lung carcinoma accounts for about 80% of all lung cancers. This type is usually treated with surgery, while small cell lung carcinoma responds better to chemotherapy and radiation. The most common cause of lung cancer is long-term exposure to tobacco smoke. About 15% of lung cancers occur in non-smokers, and is often attributed to a combination of genetic factors, and exposure to radon gas, asbestos, air pollution and second-hand smoke.
Lung cancer may be seen on a chest radiograph and CT scan. A definitive diagnosis is confirmed with a biopsy. Treatment and prognosis depends on the type of cancer, the stage (or degree it has spread) and the patient’s performance status. Survival rates vary, depending on the stage, overall health of the patient and other factors. The lungs are also a common place for metastasis of tumors from other parts of the body. Secondary cancers are classified by the site of origin; e.g., breast cancer that has spread to the lung is still called breast cancer, prostate cancer that has spread to the lung is still called prostate cancer. In children, the majority of lung cancers are secondary. Primary lung cancers themselves most commonly metastasize to the adrenal glands, liver, brain, and bone.
Some symptoms of lung cancer include:
shortness of breath
Chronic coughing
Wheezing
Coughing up blood
Chest pain or pain in the abdomen
Unexplained weight loss
Fatigue
Hoarse voice
Loss of appetite
Difficulty swallowing
Clubbing of the fingernails (uncommon)
Prior to the 1930s, lung cancer was not common, but increased dramatically over the following decades as cigarette smoking became more popular. Today, the incidence of lung cancer is beginning to fall in many countries due to public education about the dangers of cigarette smoking and the introduction of effective smoking-cessation programs. Nevertheless, lung cancer remains among the most common types of cancers in both men and women worldwide.
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