[Pigmented villonodular synovitis. Diffuse and localized forms in children]

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.

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.

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.