Lung cancer cells. Coloured scanning electron micrograph (SEM) of lung cancer cells. Cancer cells divide rapidly in a chaotic, uncontrolled manner. They may clump to form tumours, which invade and destroy surrounding tissues. Lung cancer is a common form of cancer, frequently associated with smoking tobacco and exposure to industrial air pollutants. It causes a cough and chest pain and may spread to other areas of the body. Treatment includes removal of part or all of the affected lung, with radiotherapy and chemotherapy. Magnification unknown.