Examqo › Examqo library › Orthopedic surgery › Bone tumours · IMLE

Osteosarcoma and Ewing sarcoma

These are the two common primary malignant bone tumours of children and adolescents: osteosarcoma makes bone in the metaphysis around the knee, and Ewing sarcoma is a small round blue cell tumour of the diaphysis and pelvis; both are treated with chemotherapy before and after surgery.

לקריאה בעברית

Why it matters in the exam

The classic question presents an adolescent with knee pain lasting weeks, worse at night and unrelated to effort, sometimes with swelling. In osteosarcoma the radiograph shows a mixed, destructive, bone-forming lesion in the metaphysis of the distal femur, proximal tibia or proximal humerus, with a sunburst reaction and a Codman triangle, and alkaline phosphatase is raised. In Ewing sarcoma the patient is slightly younger, the lesion is in the diaphysis or pelvis, destruction is permeative with an onion-skin reaction and a large soft tissue mass, and there may be fever, a raised sedimentation rate and leukocytosis — so the picture mimics osteomyelitis. On pathology Ewing sarcoma expresses CD99 and in most cases carries the translocation t(11;22) with the EWSR1-FLI1 fusion. Both tumours spread mainly to the lungs, so chest CT is part of the work-up. Risk factors for osteosarcoma include hereditary retinoblastoma, Li-Fraumeni syndrome, previous radiation and, in older adults, Paget disease. Treatment includes neoadjuvant chemotherapy, limb-sparing surgery when possible and adjuvant chemotherapy; a good response (necrosis of 90% or more in the resected tumour) predicts a better prognosis. Ewing sarcoma is radiosensitive, so radiotherapy is an alternative or an addition at sites where surgery is difficult, such as the pelvis. Follow-up after treatment includes chest radiographs or chest CT and limb examination over years, to detect local recurrence or metastases early.

Key points

Osteosarcoma — metaphysis around the knee, sunburst, raised alkaline phosphatase.
Ewing sarcoma — diaphysis and pelvis, onion skin, fever and inflammatory markers.
Ewing sarcoma: CD99 and translocation t(11;22).
Metastases mainly to the lungs; chest CT in every work-up.
Chemotherapy, limb-sparing surgery and, in Ewing sarcoma, sometimes radiotherapy.

Summary table

Feature	Osteosarcoma	Ewing sarcoma
Age and site	Adolescents in the growth spurt; metaphysis around the knee and proximal humerus	Age 5–20; diaphysis of long bones and pelvis
Radiograph	Mixed bone-forming lesion, sunburst and Codman triangle	Permeative destruction, onion skin and a large soft tissue mass
Laboratory and pathology	Raised alkaline phosphatase; malignant cells producing osteoid	Fever and raised sedimentation rate; small round blue cells, CD99, t(11;22)
Treatment	Chemotherapy (MAP), limb-sparing surgery, adjuvant chemotherapy	Chemotherapy, surgery and/or radiotherapy (radiosensitive)
Metastases and prognosis	Lungs; survival of about 65–70% in localised disease	Lungs and bone; similar survival in localised disease, poor with metastases

In the full version for subscribers

A simple algorithm
Memory aid
Exam traps
5 review cards
Enough for IMLE

The full version is open to subscribers of: Orthopedic surgery, Medical licensing exam (IMLE), Oncology, Pediatrics.

Subscriber? Read the full topic Plans and prices 25 free questions

Sources

Campbell's Operative Orthopaedics, 14th ed. (2021) — Malignant Tumors of Bone
ESMO-EURACAN-GENTURIS Clinical Practice Guidelines, 2021 — Bone Sarcomas
NCCN Clinical Practice Guidelines in Oncology, 2024 — Bone Cancer

Sources are given for further reading; the text is written afresh and not copied from them.

Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.