Bone cancer. Light micrograph of a section through bone tissue in a case of osteosarcoma (bone cancer). Cell nuclei are stained dark purple. Cancerous cells (the ones with large and irregularly shaped nuclei) have produced regions of disordered bony filaments (osteoids, light pink). Several of these osteoid regions are seen across bottom and at right. This highly malignant cancer, more common in young people, usually starts in a long bone and spreads rapidly. To prevent spread, removal of part of the affected bone or even amputation of the limb may be required.