Pigmented villonodular synovitis (PVNS) is a locally
aggressive synovial tumor. There are two forms of PVNS: diffuse and nodular.
Nodular occurs most commonly in the hands and diffuse is found most commonly
in the knee. PVNS may also occur in the hips and ankle. PVNS has the highest
prevalence during the third and fourth decades and it affects males and
females equally. It presents as a painless or mildly painful joint with
The radiological appearance of PVNS depends on the location. A nodule
in the hand may have soft tissue swelling and bone erosion on plain x-ray.
The knee usually only has a soft tissue mass but bone erosion or cysts
will be present in tighter joints like the hip, elbow, ankle or wrist.
The joint space is
usually preserved and there may be an effusion. CT scan is able to pick
up the hemosiderin and demonstrates the extent of the synovial involvement
as well as bone erosion and cysts. Hemosiderin appears as low or absent
signal on both T1 and T2 weighted images.
On gross examination, the diffuse form of PVNS is
a tan mass of villi and folds of synovium. The lesion may be sessile or
have several pedunculated nodules. Bony invasion through the joint capsule
is possible. The local form of PVNS is a pedunculated firm nodule.
Microscopically, PVNS is characterized by synovial
cell hyperplasia both on the surface and below the synovium. Also present
are scattered giant cells, hemosiderin and foam cells. The location of
the polyhedral cells below the synovial membrane suggests that perhaps
the cell of origin is a fibrohistiocyte. The pathologic differential includes
hemosiderotic synovitis, rheumatoid arthritis and synovial chondromatosis.
Treatment of PVNS is surgical excision. Recurrences
are common due to the difficulty of complete surgical excision.
l Bullough, Peter, Orthopaedic Pathologv (third edition), Times
Mirror International Publishers Limited, London, 1997.
Huvos, Andrew. Bone Tumors: Diagnosis. Treatment and Prognosis,
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Bravo, SM et al., Pigmented Villonodular synovitis, Radiologic
Clinics of North America, 34(2):311-325, March, 1996.