Ewing sarcoma

📖 About

• Ewing sarcoma is a rare, aggressive primary bone tumour, usually affecting children <15 years old.
• It is the second most common malignant bone tumour in children after osteosarcoma.

🧬 Aetiology

• Typical age: 5–15 years (younger than osteosarcoma).
• Arises from primitive neuroectodermal cells (neural crest origin).
• 💠 Classic cytogenetic feature: t(11;22)(q24;q12) translocation → EWSR1–FLI1 fusion gene.

🩺 Clinical Features

• 📍 Most common sites: long bones (femur, pelvis, tibia), ribs, and flat bones.
• 🩸 Localised pain and swelling (often mistaken for trauma).
• 🧱 Palpable mass or restricted movement near affected joint.
• 🌡️ Systemic “B symptoms”: fever, night sweats, weight loss.
• 🔄 Can mimic osteomyelitis – pain, fever, ↑ inflammatory markers.

🔎 Investigations

• Blood tests: FBC, U&E, ESR/CRP, ALP, LDH (↑ LDH = poor prognosis).
• X-ray: Classic “onion skin” periosteal reaction 🧅 (layered new bone).
• MRI: Defines local tumour extent; differentiates from infection.
• Histology: Sheets of small round blue cells 🔬.
• Genetics: EWSR1–FLI1 fusion gene (t[11;22]) confirms diagnosis.
• Metastasis screening: CT chest, bone scan, PET for lung/bone mets.

💊 Management

• Chemotherapy: 🚑 Induction chemo (often vincristine, doxorubicin, cyclophosphamide, ifosfamide, etoposide).
• Local control:
  • 🔦 Radiotherapy – Ewing is radiosensitive (unlike osteosarcoma).
  • ✂️ Surgery – resection or limb-salvage where feasible.
• Combined modality therapy (chemo + surgery/radiotherapy) gives best outcomes.

📈 Prognosis

• Overall 5-year survival for localised disease ≈ 60–70% 🌟.
• With metastases at presentation: <30% ❌.
• Poorer outcomes with pelvic/axial disease, large tumour volume, or high LDH.

🧑‍🏫 Exam Tip

Ewing sarcoma vs osteosarcoma: - 🧅 Onion skin X-ray (Ewing) vs 🌞 Sunburst pattern (Osteosarcoma). - 📉 Ewing is radiosensitive, Osteosarcoma is radio-resistant. - 📍 Ewing often involves diaphysis; Osteosarcoma prefers metaphysis.

Cases — Ewing Sarcoma

• Case 1 — Teenager with bone pain 🦴: A 14-year-old boy presents with progressive pain and swelling in his right femur. Exam: tender, warm swelling over the diaphysis. X-ray: permeative “moth-eaten” lesion with onion-skin periosteal reaction. MRI: soft tissue extension. Diagnosis: Ewing sarcoma of femoral shaft. Managed with neoadjuvant chemotherapy followed by surgery and radiotherapy.
• Case 2 — Pelvic tumour 🚨: A 12-year-old girl presents with pelvic pain, limp, and urinary frequency. Exam: large pelvic mass. Imaging: destructive iliac lesion with periosteal reaction; biopsy confirms small round blue cell tumour with EWSR1 gene translocation. Diagnosis: Ewing sarcoma of pelvis. Managed with chemotherapy, surgery if resectable, and radiotherapy.
• Case 3 — Metastatic presentation 🌬️: A 16-year-old boy presents with rib pain, weight loss, and cough. Exam: tender chest wall swelling. CT: destructive rib lesion with large soft tissue mass and lung metastases. Diagnosis: Ewing sarcoma of rib with pulmonary metastases. Managed with systemic chemotherapy, local radiotherapy, and palliative surgical options as appropriate.

Teaching Point 🩺: Ewing sarcoma is a highly malignant small round blue cell tumour, second most common bone cancer in children/adolescents. Typical sites: pelvis, femur, tibia, ribs. X-ray: permeative lytic lesion, onion-skin periosteal reaction. Histology/genetics: EWSR1-FLI1 translocation. Management: multi-agent chemotherapy + local control with surgery/radiotherapy. Prognosis worse if metastases present.