Pigmented villonodular synovitis (PVS) is characterized by a locally aggressive synovial proliferation that engenders progressive destruction of cartilage and bone. Two cases, a diffuse and a localized form, are reported.
Case report: 1) A 9.9-year-old boy followed up for a popliteal cyst presented with chronic arthritis of the left knee. Aspiration yielded a bloody synovial fluid. MRI showed a heterogeneous synovial process with decreased signal in both T1- and T2-weighted images. The diagnosis of PVS was made on histology of an excisional biopsy. A complete open synovectomy was then performed. 2) A 13.8-year-old boy had a palpable mass on the internal side of the right patellofemoral joint. MRI showed a heterogenous mass with areas of hypointensity on all spin echo sequences corresponding to hemosiderin deposits suggestive of PVS. Surgical excision of a reddish-brown circumscribed lesion was performed. Diagnosis of PVS was made at surgery and confirmed by histologic examination.
Conclusion: PVS diagnosis is frequently delayed due to nonspecific symptoms. Bloody fluid aspiration and MRI are valuable tools for early diagnosis. Treatment is surgical: extensive synovectomy for the diffuse form, excision of the lesion for the localized form.