Ewing Sarcoma Locations
The most common primary sites of Ewing sarcoma are the pelvic bones, femur, and bones of the chest wall, with approximately 50% occurring in the extremities and 20% in the pelvis. 1
Primary Skeletal Locations
Most Common Sites
- Pelvic bones represent one of the three most frequent primary sites 1
- Femur is the second most common location 1
- Chest wall bones (ribs and scapula) constitute the third major site 1
- Any bone may be affected, though the above sites predominate 1
Distribution Pattern
- 50% of patients have extremity tumors 1
- 20% have pelvic tumors 1
- The remaining 30% occur in axial skeleton including spine, chest wall, and other locations 1
Location Within Long Bones
- When arising in long bones, the diaphysis (shaft) is the most frequently affected site 1
- Metadiaphyseal locations are also common 2, 3
- This contrasts with osteosarcoma, which typically affects the metaphyseal region 4
Extraosseous Presentations
- Approximately 20% of cases emerge from extraosseous (soft tissue) locations 1
- Extraosseous sites include paravertebral regions, chest wall soft tissues, and other locations 3
Atypical Locations
While less common, Ewing sarcoma can occur in atypical sites including:
- Metatarsal bones 3
- Scapula 3
- Paranasal sinuses 3
- Intracranial soft tissue 3
- Spine and sacrum (associated with significantly worse prognosis) 1
Clinical Implications of Location
Prognostic Significance
- Distal/peripheral sites indicate favorable prognosis 1
- Pelvic localization is an adverse prognostic factor 1
- Spine and sacrum locations are associated with significantly worse outcomes compared to other primary sites 1
- Axial skeleton involvement generally portends poorer prognosis than extremity disease 5
Age and Demographics
- Ewing sarcoma occurs predominantly in adolescents and young adults (AYAs) with a median age of 14 years 1
- 90% of patients are under 20 years of age 1
- The incidence is approximately 1 case per 1.5 million 1
Critical Diagnostic Considerations
Imaging Characteristics by Location
- Bone appears mottled on imaging regardless of location 1, 2
- Classic "onion skin" periosteal reaction is characteristic 1, 2
- Large soft tissue component typically dominates the presentation 1
Important Pitfall
Any patient with radiological findings suggesting Ewing sarcoma must be referred immediately to a specialized bone sarcoma center before biopsy to prevent tissue plane contamination and optimize limb-salvage outcomes 4, 6. The radiosensitive nature of the disease and tendency to arise in the axial skeleton make local treatment particularly challenging 5.