Lung cancer is considered a type of tumor of the bronchial tubes and lungs. But a serious type. The initial lung cancer will be the small cubes. If left to grow cubes spread replace normal lung parenchyma. And spread to other organs such as liver, brain, bone. Occurs because of toxic residues are in the respiratory system. Or the lung. The main causes of occurrence of lung cancer there are three reasons. Firstly, because in the cigarette smoke, radon and air pollution.