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Cancer cell division. Coloured scanning electron micrograph (SEM) of a lung cancer cell in the final stage of cell division (cytokinesis). During this stage the cytoplasm of the two daughter cells divides. Here the cells remain joined by a cytoplasmic bridge (centre). 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. Magnification: x10,000 at 6x7cm size. (KEYSTONE/SCIENCE PHOTO LIBRARY/STEVE GSCHMEISSNER)