Clear Cell Sarcoma
Synonyms: Melanoma of soft parts, clear cell sarcoma of tendons and aponeuroses
Distinct entity from cutaneous melanoma despite similar IHC profile
Quick Facts
Behaviour
Malignant
Category
Soft tissue
Grade
High
Synonyms
- Melanoma of soft parts
- clear cell sarcoma of tendons and aponeuroses
Category
Soft tissue
Behaviour
Malignant
Grade
High
Gender
M = F
Tissue of Origin
Neural crest (melanocytic differentiation)
Epidemiology
- Rare, 1% of soft tissue sarcomas
- Peak incidence in young adults (2nd–4th decades)
- No significant sex predilection
- Association with tendons and aponeuroses
Clinical Features
- Slowly growing deep soft tissue mass, often attached to tendon
- Pain or tenderness in 50%
- Often misdiagnosed as Benign nodule initially
- May have satellite nodules
Location
- Foot and ankle (most common)
- Lower extremity (knee, thigh)
- Upper extremity
- Deep to skin, attached to tendons/fascia
Imaging
- Well-defined deep mass on MRI
- Iso- to hypointense on T1, heterogeneous on T2
- Variable enhancement
- FDG-avid on PET-CT
Pathology
- Nests of clear/pale cells with vesicular nuclei
- Melanin pigment in 50%
- S100, HMB45, melan-A positive (melanocytic differentiation)
- EWSR1-ATF1 or EWSR1-CREB1 fusion gene
Genetics
- EWSR1-ATF1 fusion (90%)
- EWSR1-CREB1 fusion (10%)
- These distinguish from melanoma (which lacks EWSR1 rearrangement)
Treatment
- Wide local excision with clear margins
- Sentinel lymph node biopsy considered (lymph node metastasis more common than other STS)
- Chemotherapy limited activity
- Targeted therapy: NTRK inhibitors, checkpoint inhibitors - under evaluation
Prognosis
- 5-year survival 50%
- Lymph node and distant metastasis common
- Late metastasis possible
- Prognosis worse than melanoma stage-for-stage
Key Points
- Distinct entity from cutaneous melanoma despite similar IHC profile
- EWSR1 rearrangement essential for diagnosis - melanoma lacks this
- Lymph node involvement more common than most STS - sentinel node biopsy should be considered
- Foot/ankle location in young adults is characteristic
Workup - Blood Tests
FBC, U&E, LFTs - baseline and pre-chemotherapy
Workup - Local Imaging
MRI primary site with gadolinium - local staging
Workup - Biopsy
- Core needle biopsy - confirm diagnosis
- IHC: S100+, Melan-A+, HMB-45+, SOX10+ (melanoma-like profile)
- EWSR1-ATF1 FISH (t(12;22)) - present in 90%; diagnostic
- Histology: nested clear cells with nested architecture
Workup - Staging
- CT chest/abdomen/pelvis - metastatic disease
- PET-CT - staging
Workup - Other
- MDT at soft tissue sarcoma centre
- Melanoma-like immunophenotype - diagnose by molecular EWSR1-ATF1 fusion
Follow-up Summary
- 1
Post-op visit at 6 weeks
- 2
Year 1–2
3–4 monthly clinical review + CXR; MRI primary site at 3 months then 6-monthly
- 3
CT chest every 3–4 months for 2 years; consider lymph node surveillance (LN metastasis >30%)
- 4
Sentinel lymph node biopsy results guide regional surveillance strategy
- 5
Year 3–5
6-monthly clinical review + CXR; CT chest 6-monthly
- 6
Year 6–10
Annual clinical review + CXR; CT chest annually
- 7
Discharge at 10 years; late metastasis recognised - advise self-monitoring
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.