Soft Tissue Ewing Sarcoma
Synonyms: Extraskeletal Ewing sarcoma, soft tissue Ewing
Extraskeletal Ewing sarcoma is biologically identical to Bone Ewing - treated with same protocols
Quick Facts
Behaviour
Malignant
Category
Soft tissue
Grade
High
Synonyms
- Extraskeletal Ewing sarcoma
- soft tissue Ewing
Category
Soft tissue
Behaviour
Malignant
Grade
High
Gender
Male
Tissue of Origin
Neural crest / undifferentiated mesenchymal
Epidemiology
- 15% of all Ewing sarcoma tumours occur in soft tissue
- Peak incidence in 1st–2nd decades
- Slight Male predominance
- Identical molecular profile to Bone Ewing sarcoma
Clinical Features
- Rapidly growing painful soft tissue mass
- May arise at any site - paraspinal, chest wall, extremity
- Systemic symptoms less common than Bone Ewing
- Fever and elevated ESR/CRP in some cases
Location
- Paravertebral and chest wall
- Extremities (Lower > upper)
- Retroperitoneum
- Head and neck
Imaging
- Large heterogeneous soft tissue mass
- No Bone involvement in extraskeletal form
- MRI: heterogeneous, Variable necrosis
- FDG-avid on PET-CT
Pathology
- Small round blue cell tumour - uniform cells with little cytoplasm
- CD99 (MIC2) diffuse membranous positivity (essential)
- NKX2.2 nuclear positivity
- EWSR1 rearrangement (most commonly EWSR1-FLI1 or EWSR1-ERG)
Genetics
- EWSR1-FLI1 (t(11;22)(q24;q12)) in 85%
- EWSR1-ERG in 10%
- Other rare EWSR1 fusions (ETV1, ETV4, FEV)
- RNA sequencing may detect fusions not found by FISH
Treatment
- Multiagent chemotherapy: VAC/IE (vincristine, doxorubicin, cyclophosphamide alternating with ifosfamide, etoposide)
- Local control: surgery and/or radiotherapy
- High-dose chemotherapy with stem cell rescue for High-risk/metastatic disease
- Newer agents: TK216 (in trials)
Prognosis
- 5-year survival 60–70% for localised disease
- Metastatic disease: 25–30% 5-year survival
- Pulmonary metastasis most common
- Extraskeletal Ewing generally has similar prognosis to Bone Ewing
Key Points
- Extraskeletal Ewing sarcoma is biologically identical to Bone Ewing - treated with same protocols
- CD99 is Highly sensitive but not specific - EWSR1 FISH required for definitive diagnosis
- RNA-seq increasingly replacing FISH for fusion detection
- Large tumour volume and metastases at presentation are adverse prognostic factors
Workup - Blood Tests
- FBC, U&E, LFTs, Bone profile - baseline and pre-chemotherapy
- LDH - prognostic marker
- C-reactive protein, fibrinogen - baseline inflammatory markers
Workup - Local Imaging
- MRI primary site with gadolinium - local staging; heterogeneous soft tissue mass with Variable necrosis
- CT chest/abdomen/pelvis - metastatic staging (pulmonary metastases most common)
- PET-CT - FDG avid; systemic staging
- Bone scan or whole-body MRI - skeletal staging
Workup - Biopsy
- Core needle biopsy at sarcoma centre - en bloc excision of tract
- CD99 (MIC2) diffuse membranous+ (essential)
- EWSR1-FLI1 or EWSR1-ERG FISH - diagnosis confirmation (85% and 10%)
- RNA-seq if FISH negative - detects other EWSR1 fusions
Workup - Staging
- CT chest/abdomen/pelvis - metastases
- PET-CT - systemic staging
Follow-up Summary
- 1
Years 1–2
3–4 monthly clinical review + CXR; MRI primary site at 3 months post-op then 6-monthly
- 2
CT chest every 3–4 months for first 2 years (pulmonary metastasis is primary concern)
- 3
Years 3–5
6-monthly clinical review + CXR; CT chest 6-monthly
- 4
Years 6–10
Annual clinical review + CXR; CT chest annually
- 5
Discharge at 10 years after treatment
Medical disclaimer
The content on Sarcopedia is for educational and informational purposes only and does not constitute medical advice. It is not intended to be a substitute for professional medical diagnosis or treatment. Always consult with a qualified physician regarding any health concerns or before starting any new treatment. Reliance on any information provided on this site is solely at your own risk.