Synovitis, Pigmented Villonodular

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Basics

Description

  • Pigmented villonodular synovitis (PVNS), also known as tenosynovial giant cell tumor (TGCT), is a benign proliferative and inflammatory disease associated with synovial hypervascularity; traditionally thought to be an inflammatory disease; some consider PVNS to be a benign neoplasm.
  • Classically, PVNS presents with a single nodule or multiple nodules along a synovial layer or tendon sheath containing hemosiderin deposits, macrophages, and multinucleated giant cells.
  • Two forms of PVNS exist.
    • Diffuse pigmented villonodular synovitis (DPVNS)
    • Localized pigmented villonodular synovitis (LPVNS)-focal pedunculated lesions

Epidemiology

Incidence
  • Annual U.S. incidence 1.8 cases per million
  • Predominant age: 20 to 50 years
  • There are no definite sexual, environmental, genetic, ethnic, or occupational associations; however, a history of preceding trauma with bleeding into the affected joint has been observed.

Geriatric Considerations
Rare in elderly patients

Pediatric Considerations
Rare in children

Etiology and Pathophysiology

  • Exact cause is unknown.
  • History of trauma is noted in up to 56% of patients with PVNS.
  • Hypothesized to be caused by joint trauma with bleeding into joint with subsequent development of hemosiderin deposits and inflammatory markers causing joint destruction
  • Histologic findings showing increased cellularity and the tendency to recur after treatment support neoplastic etiology. Recurrent bleeding into joint spaces leading to cartilage destruction and osteoarthritis is the natural progression in diseases such as hemophilia, which supports the above hypothesis; however, the pathophysiology is still unclear.
    • Histologically, LPVNS and DPVNS have similar features: Hemosiderin-loaded macrophages give the typical brown or “pigmented” color.
    • Multinucleated giant cells with osteoclastic features
    • Lipid-laden macrophages
  • DPVNS and LPVNS differ in their disease course.
    • DPVNS (more common than LPVNS)
      • Characterized by involvement of most or all the joint synovium with multiple nodules along synovial layer or tendon sheath with associated edema and pain
      • Rapidly destructive, with poorer prognosis compared to LPVNS
      • Potentially encroaches on neurovascular structures due to extra-articular progression complicating surgical resection, however, usually remains intra-articular
      • Continued inflammation and joint erosions lead to articular cartilage destruction and subsequent osteoarthritis.
    • LPVNS
      • Characterized by a single discrete or pedunculated nodule
      • Favorable prognosis due to localized nature
      • Low recurrence rate postoperatively

Genetics
  • t(1;2)(p12;q35) is a translocation of collagen 6A3 (COL6A3) gene and macrophage colony-stimulating factor 1 (CSF1) gene. It has been found in a fraction of tumor cells.
  • This mutation causes an overexpression of CSF1 (a.k.a. macrophage colony-stimulating factor 1), which activates and recruits its receptor (CSF1R), which is usually found in monocytes and macrophages in PVNS nodules.
  • The presence of proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) has been recently discussed with regard to therapeutic modalities and use of monoclonal antibodies for treatment of refractory PVNS.

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