Coloured scanning electron micrograph (SEM) of an abnormal set of chromosomes from a patient suffering from osteosarcoma (bone cancer). Any normal human cell contains 46 chromosomes, whereas this abnormal cell contains many more. Osteosarcoma is usually seen in children and adolescents, but can occur in adults, particularly in association with Paget's disease. The primary tumour usually occurs in the leg bones, but abnormal cells are often spread in the bloodstream, and secondary growths (metastases) are common. Magnification: x860 at 6x6cm size.