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Pigmented Villonodular Synovitis

 

Pigmented villonodular synovitis is sometimes called PVNS. PVNS is a slow growing, benign, reactive synovial proliferation characterized by proliferation of pigment laden histiocytes and giant cells. PVNS occurs in the middle age, and it can be localized or diffuse. Localized occurs predominantly in the anterior knee (classic) and will have less recurrence. The lesion is usually intra-articular, with or without extra-articular extension. If it occurs extra-articular, this is called “giant cell tumor of the tendon sheath”, and this is not related to giant cell tumor of the bone. Giant cell tumor of the tendon sheath is a superficial soft tissue small nodule that is painless, usually affecting the hand, the wrist, and the feet (occurs extra-articular from the beginning). PVNS is intra-articular. The patient complains of unilateral, spontaneous intermittent pain, swelling, and effusion with decreased range of motion. The patient may complain of recurrent hemorrhagic effusion, so with aspiration of the knee there will be brownish or bloody fluid. It usually occurs predominantly in the knee (about 80%) and this is followed by the hip. You may feel a boggy soft tissue mass in the knee or behind the knee. The PVNS tumor may infiltrate and erode bone, extending into the soft tissue surrounding the involved joint. When you look at the x-ray, you may find well defined erosions, such as osteolytic changes on both sides of the joint. The PVNS probably is a diffuse, advanced disease. MRI will show soft tissue masses and effusion due to synovial proliferation. The lesion can be localized or nodular. You will find nodular lesions inside the joint, usually the anterior knee. There will be low intensity signal in T1 and in T2 MRI due to hemosiderin deposition. This MRI signal is characteristic of PVNS. You can also see a diffuse process in the MRI, especially if it involves the posterior compartment (anterior and posterior compartments). The PVNS lesion can also extend beyond the joint with erosions of the joint. A differential diagnosis is giant cell tumor, the primary bone tumor (lesion is inside the bone). Another differential diagnosis is synovial cell sarcoma, a soft tissue sarcoma with translocation X; 18. It can occur near the joint and rarely is found intra-articular (does not have giant cells). Synovial chondromatosis occurs due to metaplasia of the cartilage inside the synovium. The patient will complain of knee pain, swelling, and locking. X-ray and MRI will show multiple calcified loose bodies (rice bodies) inside the joint. Chondroid tissue in synovial tissue. Treatment is complete arthroscopic synovectomy. Hemophilia (hemophilic arthropathy) is usually bilateral familial disease. The pathology is a gross appearance. Redish/brownish stained synovium with extensive papillary projections. Microscopic histology will show mononuclear stroma with histiocytes infiltrating the synovium with hemorrhage and hemosedrine pigments (macrophages with giant cells in the field). To treat focal or nodular, do excision (arthroscopic or open). To treat diffuse, do total synovectomy (open, arthroscopic, or combined). To treat combined, do anterior arthroscopic or do posterior open; you will have lower recurrence rate. PVNS has a high local recurrence. Sometimes you use radiation if the patient has multiple local recurrence. If the tumor is a giant cell tumor of the tendon sheath (hand, fingers, or feet) do marginal excision.

Author
Nabil Ebraheim, MD

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