Malignant bone tumor arising from neuroectodermal cells.- Associated with translocation t(11;22) (fusion protein EWS-FLI1)

- Most common in Caucasians- Generally boys < 15 years old

Symptoms:- Localized pain (progressive, worsens at night), hyperthermia, and swelling after trauma to the bone - B symptoms

Localiization: Often diaphyses of long bones (particularly femur, tibia, fibula, and humerus) and bones of the pelvis

Diagnostics- X-ray: lytic bone lesions, onion skin appearance of the periosteum- Laboratory findings: ↑ ESR, ↑ LDH, leukocytosis- Biopsy: Anaplastic small-blue-round-cell malignancy; chromosomal translocation t(11;22), CD99

Treatment: Definitive resection plus neoadjuvant and adjuvant polychemotherapy