Ewing sarcoma

Ewing sarcoma

Updated: 08/12/2022

© Jun Wang, MD, PhD

General features

• AKA primitive neuroectodermal tumor (PNET)
• #2 bone sarcoma in children, after osteosarcoma
• Usually whites, ages 5-20 years
• Possible multiple lesions at presentation
• 5 year survival near 75%

Clinical presentations

• Pain, fever, weight loss

Most common sites

• Medullary cavity, usually shaft
• Femur, tibia, humerus, etc

Key pathogenesis

• EWS-Fli1 activates Cyclin D and Cyclin E
• Activation of Cyclin D and Cyclin E promotes cell cycle progression through suppression of tumor suppressor RB

Key radiologic findings

• Mottled, osteolytic lesion with sunburst periosteal reaction
• Lamellated periosteal reaction
• Codman’s triangle: Shadow between cortex and raised ends of periosteum (due to reactive bone formation), non-specific (can be seen in osteosarcoma)

Key morphological features

• Sheets of small blue cells with scant cytoplasm and round nuclei

Markers

• Positive for CD99

Differential diagnosis

• Lymphoma: Positive for CD45, CD20 if B cell, CD3, etc if T-cell, but negative for CD99
• Small cell carcinoma: Positive for cytokeratin and neuroendocrine markers such as chromogranin, synaptophysin and CD56

Genetic abnormalities

• t(11,22)(q24;q12)/EWS-FLI1

Treatment

• Surgery
• Chemotherapy
• Radiation

Back to bone tumors
Back to contents