Recurrence of pigmented villonodular synovitis of the knee 17 years after the initial treatment. A case report.

Pigmented villonodular synovitis (PVNS) is a benign proliferative process involving the synovial membranes bursas or tendon sheaths. The rarity of the process, the absence of well-documented long follow-up examinations, as well as reports on different forms of the disease from multiple anatomic sites has lead to some confusion. This is a case report of a 44-year-old woman with recurrence of PVNS of her right knee, 17 years after the initial limited knee synovectomy. It was proven impossible to differentiate the disease from soft-tissue malignancy despite the use of all the available investigation methods, including nuclear magnetic resonance. Eventually the diagnosis was made by an open biopsy. Marginal excision of the soft-tissue mass from the popliteal fossa was performed initially, followed by a total knee synovectomy within the next two weeks. The patient remains recurrence free 32 months after the operation.