Synonyms

Synovial cell sarcoma

Category

Soft tissue

Behaviour

Malignant

Grade

High

Gender

Both equally

Tissue of Origin

Other

Epidemiology

• Malignant sarcoma affecting adolescents and young adults
• Peak incidence 2nd-3rd decades
• Predilection for extremities
• Monoarticular near large joints
• t(X;18) EWSR1-SS18 translocation diagnostic

Clinical Features

• Painful mass near large joint
• Rapid growth
• Limited joint motion
• Constitutional symptoms if metastatic

Location

• Knee (most common)
• Ankle
• Shoulder
• Elbow
• Wrist

Imaging

• MRI: heterogeneous mass near joint
• T2: cystic areas and hemorrhage common
• Calcification rare but characteristic

Pathology

• Biphasic (epithelial + spindle) or monophasic variants
• t(X;18) EWSR1-SS18 fusion pathognomonic
• SS18+ (nuclear immunostain)
• High-grade sarcoma

Genetics

• t(X;18)(p11;q11) EWSR1-SS18 90%
• t(X;18)(p11;q11) EWSR1-SSX2 5-10%
• Rare other rearrangements

Treatment

• Wide surgical resection: primary treatment
• Chemotherapy: neoadjuvant or adjuvant
• Radiotherapy: adjuvant if margins inadequate

Prognosis

• 60-70% 5-year survival with multimodal therapy
• Stage and size prognostic factors
• High metastatic potential

Key Points

• t(X;18) EWSR1-SS18 fusion diagnostic
• Multimodal therapy standard
• High-grade malignancy despite small appearance

Workup - Blood Tests

FBC, U&E, LFTs, LDH

Workup - Local Imaging

• MRI primary site: local staging
• CT chest/abdomen/pelvis: metastatic staging
• PET-CT: consider

Workup - Biopsy

Core needle biopsy: EWSR1-SS18 FISH confirmatory

Workup - Staging

CT chest/abdomen/pelvis: standard

Follow-up Summary

• Year 1: Post-operative visit within first 6 weeks; 3–4 monthly clinical examination and CXR; image prosthesis at 6 months and 1 year
• Year 2: 3–4 monthly clinical examination and CXR; image prosthesis annually
• Years 3–4: 6-monthly clinical examination and CXR; image prosthesis annually
• Years 5–10: Annual clinical examination and CXR; image prosthesis annually
• Discharge at 10 years after treatment