Bone cancer cell. Coloured scanning electron micrograph (SEM) of bone cancer precursor cell (blue). This cell is a monocytes, immune cell that circulate in the blood prior to entering tissues where it develops into a macrophage cell. Several macrophage cells will later join together to form a large, multi- nucleated cell called an osteoclast. Osteoclasts are normally present in bones but can become cancerous. They can develop into a giant cell tumour (osteoclastoma) or osteosarcoma, a type of bone cancer that usually affects the ends of the long bones. Magnification: x3000 when printed at 10 centimetres wide.