Ewing's sarcoma. Light micrograph of Ewing's sarcoma, a rare, malignant form of bone cancer. Darkly stained cancerous cells with large purple nuclei are seen spreading outwards in bone tissue. Ewing's sarcoma arises in large bones such as the femur, tibia, humerus and the pelvic bones. It spreads to other parts of the body at an early stage. The condition is most common in children between 10 and 15 years of age, and affects twice as many boys as girls. The affected bone is painful, tender and may also become weakened and fracture easily. It is treated using radiotherapy and anti-cancer drugs. Magnification: unknown.