Lung cancer, like all other cancers, arises when there is an abnormality in body cells. When one suffers from cancer, new cells are produced even when they not required by the body, leading to formation of a large mass of cells known as tumor. Cancer tumors can either be malignant or benign. The term “cancer” is used to refer to tumors that are malignant. Benign tumors are easy to remove and cannot spread to different parts of the body. On the other hand, malignant tumors grow very aggressively, can enter into both lymphatic and circulatory systems and they invade other tissues within the body. The process of this spread is known as metastasis and the areas where these tumors develop are known as metastases.
Once lung cancer forms, it tends to metastasize very early. This makes it a life-threatening form of cancer and one that is very difficult to treat. Although lung cancer can spread to any part of the body, the areas that are most commonly affected my metastases include liver, adrenal glands, brain and bone tissue.
Lung cancers can attack any part of the lung. However, 95 % of all lung cancers are commonly thought to affect epithelial cells. Epithelial cells are found in the lining of bronchi and bronchioles (Ihde, 1997). This is the main reason why lung cancers are often referred to as bronchogenic carcinomas or bronchogenic cancers. Sometimes lung cancers may affect the pleura and rarely the supporting tissues of the lung such as blood vessels.
Lung cancer is the greatest cause of death due to cancer all over the world. In December 2008, the American Cancer Society’s estimated that 219,440 new lung cancer cases were going to be diagnosed and that 159,390 lung cancer-related deaths were going to occur in 2009. The U.S National Cancer Institute approximates that one in every 14 Americans will suffer from lung cancer at one point in their lifetime. Lung cancer mostly affects elderly people; about 70% of all people diagnosed with the disease are above 65 years old while less than 3% of all cancer cases are reported among people who are below 45 years of age (Jemal, 2005).
Doll & Hill (1956), report that lung cancer was not very common before the 1930s. However, in the decades that followed, the disease became more prevalent as more people started smoking tobacco. In many developing countries, incidents of lung cancer have begun to reduce as a result of public education programs on the dangers of smoking. Nevertheless, lung cancer remains the most commonly occurring type of cancer the world over. In the U.S, this type of cancer has even surpassed breast cancer among women as the main cause of cancer-related deaths.