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Pigmented Villonodular Synovitis

Definition

  • A locally aggressive synovial tumour which affects both large joints & tendon sheaths
  • Same entity as giant cell tumour of tendon sheath

Terminology

  • Other names for this disorder have included
    • synovial xanthoma
    • synovial fibroendothelioma
    • synovial endothelioma
    • benign fibrous histiocytoma
    • xanthomatous giant cell tumour
    • myeloplaxoma
    • chronic haemorrhagic villous synovitis

Epidemiology

  • 1.8 per million
  • No sex or racial predilection
  • Most common in the 20s & 30s

Aetiology

  • Essentially unknown
  • Theories
    • Hirohata
      • localized disturbance in the metabulism of lipids
    • Trauma.
      • However, low incidence in patients with haemorrhagic disorders, & has not been consistently reproduced in experimental animals
    • Inflammation
      • Widest held theory since 1941 (Jaffe)
      • Trigger for inflammation has not been identified

Pathology

Gross

  • Tan colour
  • In the knee usually consists of multiple nodules, often with dramatic associated hyperplastic villous changes in the synovium, giving a straggly beard appearance
  • Extensive haemosiderin deposition

Microscopic

  • Pruliferating, cullagen producing pulyhedral cells
  • Often scattered multinucleated giant cells
  • Foam cells
  • Haemosiderin

Clinical presentation

  • Much more frequently found as a sulitary nodule & more rarely as a diffuse multinodular condition
  • Most common sites are the knees & fingers
  • Can also occur in the wrist, hip, ankle & toes
  • Usually painless or only mildly painful. Onset is insidious
  • Approximately 50% can recall an episode of trauma

Signs

  • Local warmth
  • Swelling
  • Stiffness
  • Palpable mass
  • Point tenderness in 50%

Investigations

Aspiration

  • produces a deep xanthochromic to brownish stained bloody fluid

Xray

  • Fingers
    • usually only soft tissue swelling or there may be cortical erosion
  • Knee
    • major finding is soft tissue swelling which may be massive
  • Erosion may cause a lytic intramedullary lesion. Erosion is rare in the knee because a substantial bulk of tumour can be accommodated, but is more common in the hip
  • Lucencies on either side of a joint are very characteristic of PVNS
  • Findings of extension outside the joint, calcification or cortical destruction suggest the diagnosis of synovial sarcoma

MRI

  • low to intermediate signal intensity on T1 & T2 weighted images

Treatment

  • Excision
    • Options
      • arthroscopic
      • open using anterior & posterior approaches
        • In the posterior approach, a lazy S incision is made, the gastrocnemius heads are released & the capsule opened using two T shaped incisions, one medial & one lateral
        • menisci are detached both anteriorly & posteriorly & are later repaired
  • Radiation synovectomy
    • Radioculloid yttrium-90 is injected into the knee
    • Doesn’t appear to affect the knee cartilage
  • External beam irradiation
    • may be used. One dosage that has been used is 35Gy
    • Tends to be used in recurrences
  • Arthrodesis
    • End stage destruction, particularly in the ankle, often requires arthrodesis

Prognosis

  • Metastatic disease may develop
  • MRI is effective in detecting recurrence postoperatively
  • Recurrence is common in the diffuse form of the disease
  • E.g. 33% in a series of 18 patients with PVNS of the knee
  • In the localized form recurrence is uncommon
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