Lung cancer is consider tumor a kind of one of the bronchial tubes and lungs, but a serious type. The begin lung cancer will be the small cubes, If left the cubes will grow and replace normal lung. And pass to other organs such as liver, brain, bone. Occurs because of toxic residues are in the respiratory system or the lung. Did you know Lung cancer is causes by anything. The main causes of occurrence of lung cancer there are three reasons. Firstly, because in the cigarette smoke, radon and air pollution.