Summary

Ewing's Sarcoma is a highly malignant, high-grade Primary Bone Tumor arising from neuroectodermal cells. It is the second most common bone sarcoma in children (after Osteosarcoma) and is notorious for mimicking Acute Osteomyelitis (Fever, Pain, Swelling, High WCC/ESR). It typically affects the Diaphysis (Shaft) of long bones or the Pelvis. The genetic hallmark is the t(11;22) translocation. Radiologically, it presents with a permeative "moth-eaten" pattern and "Onion Skin" periosteal reaction. It is extremely Radio-sensitive and Chemo-sensitive. Treatment involves multi-agent chemotherapy followed by surgical resection or radiotherapy. [1,2]

Key Facts

• Definition: Small Round Blue Cell Tumour.
• Epidemiology: Age 5-25. White > Black/Asian (Rare in African descent).
• Genetics: t(11;22) (EWS-FLI1 fusion protein).
• Location: Diaphysis of long bones (Femur, Tibia, Fibula) or Flat bones (Pelvis, Scapula).
• Imaging: "Onion Skinning" (Lamellated periosteal reaction).
• The Mimic: Presents with systemic signs (Fever, Malaise) indistinguishable from infection.

Clinical Pearls

"Patrick Ewing's Jersey": A classic mnemonic. Patrick Ewing (NBA player) wore number 33. The translocation is 11 + 22 = 33.

"The Infection Trap": Because the child has a fever, high white cells, and a hot swollen leg, they are often treated with antibiotics for "Osteomyelitis". When it doesn't get better after 2 weeks, ONLY THEN is an X-ray taken. Rule: If "Osteomyelitis" is not responding, X-ray it.

"Diaphysis vs Metaphysis":

• Osteosarcoma: Metaphysis (End of bone).
• Ewing's: Diaphysis (Middle of bone).

"Small Round Blue Cells": The histological appearance. It looks like Lymphoma, Neuroblastoma, or Rhabdomyosarcoma. You need CD99 staining (MIC2) to prove it is Ewing's.

        CHILD WITH BONE PAIN + FEVER
                ↓
    X-RAY (Onion Skin / Permeative)
                ↓
    REFER TO SARCOMA CENTRE
                ↓
    STAGING (MRI, CT Chest, PET)
    GENETICS (Biopsy -> t11;22)
                ↓
    NEO-ADJUVANT CHEMOTHERAPY (12 weeks)
    (VAC / IE Regimen)
                ↓
        RESTAGING
        ┌───────┴───────┐
    RESECTABLE         NON-RESECTABLE
        ↓               ↓
    SURGERY          RADIOTHERAPY
    (Limb Salvage)   (Definitive)
        ↓               ↓
    ADJUVANT CHEMOTHERAPY

1. Chemotherapy (The Foundation)

• VAC/IE: Vincristine, Doxorubicin (Adriamycin), Cyclophosphamide alternating with Ifosfamide, Etoposide.
• Duration: Intensive. 9-12 months.
• Effect: Melts the tumour rapidly.

2. Local Control: Surgery vs Radiotherapy

• Surgery: Preferred if the bone can be removed without severe disability (e.g., Fibula, Rib, or limb salvageable). Better long term local control.
• Radiotherapy:
  • Ewing's is Radiosensitive.
  • Used if: Unresectable location (Pelvis, Spine), or if surgery would cause massive morbidity.
  • Risk: Secondary malignancy (Osteosarcoma) later in life. Growth plate arrest.

Reconstructing the Shaft

• If the tumour is in the mid-shaft femur, we don't need to sacrifice the knee or hip joint.
• We resect the cylinder of bone.
• We replace it with:
  1. Massive Allograft: A donor femur cylinder.
  2. Vascularised Fibula Graft: Taking the patient's own fibula (with blood supply) and putting it inside the allograft ("Capanna Technique").
  3. Custom Metal Spacer: Metal cylinder.

Key Studies

1. IESS-1 Study: Established VAC chemo.
2. Euro-E.W.I.N.G. 99: Compared different chemo regimens. VAC-IE is standard.

What is Ewing's Sarcoma?

It is a rare type of bone cancer that affects children and young adults. It usually starts in the middle of the long leg bones.

Is it an infection?

It behaves exactly like an infection - high fever, red skin, pain. That's why it is confusing. But antibiotics won't touch it. It is a tumour.

How do we treat it?

We hit it hard with Chemotherapy first. This shrinks it down. Then we usually operate to remove the bone, or use Radiotherapy beams to kill the rest.

What is the chance of survival?

If it stays in one bone, the survival is good (about 70%). If it spreads to the lungs, it is much more dangerous.