Synovial Sarcoma

Epidemiology

 

4th most common STS

- 10-35% of STS

 

Peak age 3rd-4th decade

- rare in children

 

Pathology

 

Cellular characteristics suggest tumour arises from primitive synovial cells

- rarely actually occurs within joint

 

Characteristic

 

Occasionally metastasis to lymph nodes (5-7%) 

- like Epitheloid Sarcoma 

- feel nodes in examinaiton

 

Classically show mineralization

- see on knee X-ray

 

Most common STS of foot

 

Synovial Sarcoma Foot MRI0001Synovial Sarcoma Foot MRI0002

 

Rarely intra-articular

 

Location

 

Deep soft tissues

- often centered on tendons, bursa and joints

- head, neck & trunk 15%

- extremities 50% / knee

- hands & feet 10% / often mistaken for ganglion

 

X-ray

 

May have calcification or ossification in tumour

 

DDx Soft Tissue Lump with calcification

 

Malignant ST tumour

 

Benign ST tumour - hemangioma / AVM

 

Malignant bone tumour - OS

 

Myositis Ossification

 

DDx lymph node metastasis

 

Clear cell sarcoma

Rhabdomyosarcoma

TB! - Calcified lymph node

 

MRI

 

Knee

- heterogenous mass, not communicating with joint

 

DDx Baker's cyst

- semimembranosus

- communicates with joint

- between semimebranosus tendon and medial head gastrocnemius

 

Bakers Cyst MRIBakers Cyst MRI

 

Histology

 

Difficult to grade 

- all considered high grade

- more extensive calcification suggests better prognosis

 

A. Biphasic Type

- classic pattern

- contains 2 distinct cell types

- epitheliod cells which resemble adenocarcinoma

- form gland like structures lined by cuboidal cells

- malignant spindle cells

 

B. Monophasic Type

- as common as classic biphasic

- spindle cells only 

- difficult to DDx from fibrosarcoma

 

Cytogenetics

 

Have a characteristic translocation

- t(X:18)

 

Management

 

Pre-op DXRT & Resection

 

Limb salvage may be possible

- amputation preferred in hand & foot

 

Post operative chemotherapy

 

Prognosis

 

70% 5 year survival rate

 

Metastases occur in 50%

 

Poor prognosis 

- local recurrence 

- inadequate resection 

- large size / monophasic / mets

 

Better prognosis

- heavily calcified

- <5cm