Pigmented Villonodular Synovitis

Pigmented Villonodular Synovitis

Prepared by Dr. Alper DUNKI

Pigmented Villonodular Synovitis (PVNS), also known as tenosynovial giant cell tumor (diffuse type), is a benign but locally aggressive proliferative disorder of the synovium, tendon sheaths, and bursae. It is characterized by hemosiderin deposition, multinucleated giant cells, and synovial villous nodular overgrowth. Although histologically benign, PVNS can cause significant joint destruction if untreated.

Epidemiology

• Incidence: approximately 1.8 cases per million per year.
• Most common in adults aged 30–50 years.
• Slight female predominance.
• Knee is affected in about 75% of cases, followed by hip, ankle, and shoulder.

Pathophysiology

• Thought to arise from clonal neoplastic proliferation of synovial cells driven by CSF1 gene overexpression due to a t(1;2)(p13;q37) translocation.
• Overproduction of colony-stimulating factor 1 (CSF1) recruits macrophages and giant cells, leading to synovial hyperplasia and hemosiderin deposition.
• Classified into two forms:Localized (Nodular) PVNS – affects tendon sheaths, often in the hand or foot.
  Diffuse PVNS – involves entire synovial lining of large joints, most commonly the knee or hip.

Clinical Presentation

• Gradual joint swelling, pain, and stiffness over months or years.
• Recurrent hemarthrosis (bloody effusion) is a classic finding.
• Mechanical symptoms (locking or catching) in large joints due to nodular tissue.
• In advanced disease, cartilage erosion and secondary osteoarthritis may occur.

Imaging Features

Radiographs:

• Often normal in early stages.
• Later show periarticular bone erosions with preserved joint space.

MRI (gold standard):

• Diffuse synovial thickening with low signal intensity on both T1 and T2 (due to hemosiderin).
• “Blooming artifact” on gradient-echo sequences is characteristic.
• Contrast enhancement demonstrates active synovial proliferation.

CT Scan:

• Useful to assess bone erosion and subchondral involvement.

Histopathology

• Synovial villi and nodules composed of mononuclear histiocyte-like cells, multinucleated giant cells, foam cells, and hemosiderin deposits.
• Mitotic activity is present but without atypia or malignant features.

Differential Diagnosis

Condition                                       Distinguishing Feature     

Rheumatoid arthritis :    Bilateral, symmetric, elevated serologic markers   

Hemophilic arthropathy :    History of bleeding disorder, absence of proliferative nodules   

Synovial chondromatosis :  Cartilaginous nodules visible on imaging  

Synovial sarcoma :     Malignant histology, soft-tissue mass, calcifications

Treatment

The mainstay of treatment is complete synovectomy, with the goal of eradicating diseased synovium while preserving joint function.

1. Surgical Management

• Arthroscopic synovectomy – preferred for localized or accessible diffuse disease.
• Open synovectomy – required for extensive or extra-articular extension.
• Combined approach (open + arthroscopic) may reduce recurrence in the knee.
• Joint replacement (arthroplasty) indicated in end-stage degenerative joints.

2. Adjuvant Therapies

• External beam radiotherapy (EBRT) or radiosynovectomy (Yttrium-90) can reduce recurrence after incomplete resection.
• Targeted therapy: CSF1 receptor inhibitors (e.g., Pexidartinib) are effective for unresectable or recurrent cases.

Prognosis

• Localized PVNS: recurrence <10%.
• Diffuse PVNS: recurrence 20–50%, often within 2 years.
• Delayed diagnosis or incomplete excision can lead to joint destruction requiring arthroplasty.
• Metastasis is exceptionally rare.

Key Points

• PVNS is a benign but destructive synovial tumor driven by CSF1 overexpression.
• MRI blooming artifact is a key diagnostic feature.
• Complete synovectomy remains the gold standard treatment.
• Targeted CSF1 inhibitors offer new hope for recurrent or unresectable cases.
• Localized PVNS → Arthroscopic excision gives excellent outcomes with minimal recurrence.
• Diffuse PVNS → Combined synovectomy ± adjuvant therapy provides better local control.
• CSF1R inhibitors (e.g., Pexidartinib) are now first-line for unresectable or recurrent diffuse PVNS.

References

1. Mastboom MJL, et al. Diffuse-Type Tenosynovial Giant Cell Tumor: Current Concepts and Future Perspectives. Nat Rev Rheumatol. 2021;17(6):363–376.
2. Cassier PA, et al. CSF1R Inhibition with Pexidartinib in Tenosynovial Giant Cell Tumor. N Engl J Med. 2019;379(4):341–350.
3. van der Heijden L, et al. Pigmented Villonodular Synovitis: A Review of Current Management Strategies. J Am Acad Orthop Surg. 2020;28(15)–e673.
4. Mollon B, et al. Arthroscopic vs. Open Synovectomy in PVNS: A Meta-Analysis. J Bone Joint Surg Am. 2015;97(6):522–534.
5. Murphey MD, et al. Imaging of Pigmented Villonodular Synovitis and Tenosynovial Giant Cell Tumor. Radiographics. 2008;28(5):1493–1518.

MRI Findings Summary Table

Feature	Description	Diagnostic Value
Synovial Thickening	Diffuse or nodular proliferation of synovium lining the joint capsule	Seen in both localized and diffuse PVNS
Signal Intensity (T1)	Iso- to hypointense relative to muscle	Hemosiderin deposition lowers T1 signal
Signal Intensity (T2)	Predominantly low due to hemosiderin, sometimes mixed with high areas (fibrosis vs inflammation)	“Dark on T2” pattern is characteristic
Blooming Artifact	Signal drop on gradient-echo (GRE) sequences caused by magnetic susceptibility of hemosiderin	Pathognomonic for PVNS
Contrast Enhancement	Strong enhancement of synovial tissue, absent in cystic or necrotic areas	Reflects active disease
Bone Involvement	Cortical erosion, pressure remodeling, subchondral cysts	Indicates chronic or advanced disease
Extra-Articular Extension	Seen in diffuse type (knee, hip, ankle)	Helps determine need for open approach
Joint Effusion	Usually minimal to moderate, occasionally hemorrhagic	Supports diagnosis but non-specific