What Are the Different Types of Lung Cancer and How Do They Differ

When the human body receives a cut or an injury, the cells in the skin get a natural signal prompting them to divide to form new cells which fill the injured area and heal the wound (Williams, 1992, p.3). As soon as the healing process is complete, the cells receive another message that informs them that it is time to stop dividing. Occasionally this natural mechanism of controlling cell division may become impaired in that a cell may receive the signal to begin division but not the one to stop or the cell may receive the signal to stop but may not be able to respond to it (Williams, 1992, p.3). In such a condition, the cell may be permanently or indefinitely switched on and may continue to divide indefinitely. The cells formed by the division of defective cells may themselves be defective and may also continue dividing unchecked. These cells may eventually form cancer. They may grow randomly at the site of origin initially and eventually may spread to other parts of the body by invading the local tissues through blood vessels or the lymphatic system (Williams, 1992, p.3). Cells undergo different stages of change before they totally develop into a malignant tumour. Cells that have grown abnormal but are not yet malignant or cancerous are said to be in the pre-malignant or precancerous stage. Such cells may not always develop further to become cancerous.
Cancer of the lung is commonly seen in developed, affluent countries. The risk of developing lung cancer is higher in industrialized countries than in developing countries. People living in the United Kingdom are known to have the highest risk of developing lung cancer, while this risk is lowest for people living in Nigeria (Williams, 1992, p.10). Similarly, the risk is higher for men than for women. Smoking is a very significant risk factor for lung cancer as also is exposure to carcinogens like asbestos. Other causes of lung cancer include passive smoking, tobacco use, air pollution and lung diseases such as chronic obstructive lung disease and tuberculosis (Stoppler, 2009, p.2).