Ewing sarcoma is the second most common highly malignant primary bone tumour of childhood after osteosarcoma, typically arising from medullary cavity with invasion of Haversian system. They usually present as moth-eaten destructive permeative lucent lesions in the shaft of long bones with large soft tissue component without osteoid matrix, and typical onion skin periostitis. It may also involve flat bones and appears sclerotic in up to 30% of cases.
Typically occurs in children and adolescents between 10 and 20 years of age (95% between 4 and 25 years of age), and has a slight male predilection (M:F 1.5:1) 1-2. It's rare in black people.
Presentation is non-specific with local pain being by far the most common symptom. Occasionally a soft tissue mass may be palpable. Pathological fractures also occur. Systemic symptoms including fever may be present. ESR is also elevated.
Ewing sarcoma is a small round blue cell tumour with regular sized primitive appearing cells. It is closely related to the soft tissue tumours pPNET, Askin tumour and neuroepithelioma, which collectively are referred to as Ewing sarcoma family of tumours (ESFT) 1. They share not only microscopic appearances but also demonstrate a non-random t(11;22)(q24;q12) chromosome rearrangement.
- lower limb: 45%
- femur most common
- pelvis: 20%
- upper limb: 13%
- spine and ribs: 13%
- sacrococcygeal region most common 4
- skull/face: 2%
- long bones: 50-60%
- femur: 25%
- tibia: 11%
- humerus: 10%
- flat bones: 40%
- pelvis: 14%
- ribs: 6%
As far as location within long bones, the tumor is almost always metadiaphyseal or diaphyseal 2-3:
- mid-diaphysis: 33%
- metadiaphysis: 44%
- metaphysis: 15%
- epiphysis: 1-2%
Ewing sarcomas tend to be large poorly marginated tumours, with over 80% demonstrating extension into adjacent soft tissues. It should be noted that pPNET often extend into bone, making the distinction difficult.
Plain film and CT
The appearance of these tumours is very variable, but usually have clearly aggressive appearance. Common findings include 2:
- permeative: 76%
- laminated (onion skin) periosteal reaction: 57%
- sclerosis: 40%
Soft tissue calcification is uncommon, seen in less than 10% of cases 2.
- T1: low to intermediate signal
- T1 C+ (Gd): heterogeneous but prominent enhancement
- T2: heterogeneously high signal, may see hair on end low signal striations
Ewing sarcomas demonstrate increased uptake on both Gallium67-citrate and all three phases of the Technetium99m methylene diphosphonate bone scans 6.
Treatment and prognosis
Systemic chemotherapy is the mainstay of treatment with surgery and/or radiotherapy playing a role depending of the location and size of the tumour.
What was once a uniformly fatal tumour now has respectable survival rates, although these vary with location. Spinal tumours for example have up to 86% long term survival compared to 25% of sacrococcygeal tumours 4. The overall 5 year survival is in the order of 50-75% of patients with local disease only at the time of presentation 5.
Prognosis is significantly impacted by the presence of distant metastases at the time of diagnosis, which are far more common for the pelvis (25-30%) compared to extremities (<10%) 5. Metastases most frequently go to bone or lungs.
History and etymology
It is named after James Stephen Ewing, American pathologist (1866-1943) 8.
- other Ewing sarcoma family of tumours
- osteosarcoma (ALP is not elevated in Ewing sarcoma)
- metastatic disease
- haematological malignancy
The differential diagnosis for bone tumours is dependent on the age of the patient, with a very different set of differentials for the paediatric patient.
- bone-forming tumours
- cartilage-forming tumours
- chondromyxoid fibroma
- fibrous bone lesions
- bone marrow tumours
- other bone tumours or tumour-like lesions
- aneurysmal bone cyst
- benign fibrous histiocytoma
- giant cell tumour of bone
- Gorham massive osteolysis
- haemophilic pseudotumour
- intradiploic epidermoid cyst
- intraosseous lipoma
- musculoskeletal angiosarcoma
- musculoskeletal haemangiopericytoma
- primary intraosseous haemangioma
- simple bone cyst
- impending fracture risk
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- 2. Maygarden SJ, Askin FB, Siegal GP et-al. Ewing sarcoma of bone in infants and toddlers. A clinicopathologic report from the Intergroup Ewing's Study. Cancer. 1993;71 (6): 2109-18. Pubmed citation
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- 5. Halperin EC. Pediatric radiation oncology. Lippincott Williams & Wilkins. (2005) ISBN:0781742528. Read it at Google Books - Find it at Amazon
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- 8. Ewing J. Classics in oncology. Diffuse endothelioma of bone. James Ewing. Proceedings of the New York Pathological Society, 1921. CA Cancer J Clin. 22 (2): 95-8. doi:10.3322/canjclin.22.2.95 - Pubmed citation