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


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