Pigmented villonodular synovitis responsive to imatinib therapy.

I n 2002 when he was 27 years old, our patient sought care for a 2-year history of right hip pain that he fi rst noted after jogging. Th e pain progressed to where he could not run. He saw his family practitioner, who thought it might be a hernia. Later, the pain progressed, and he was referred to an orthopaedic surgeon. He was referred to Baylor University Medical Center at Dallas for further evaluation in April 2004. At the time of this evaluation, he had no signifi cant past medical history other than a penetrating eye injury in 1983, followed by retinal surgery in 1989. He still has diffi culty with vision. He was not taking any regular medications, other than occasional nonsteroidal antiinfl ammatories for pain. On physical examination, he had a very mild coxalgic hip gait and slight limitation in the internal rotation of the right hip compared with the left. He said he occasionally felt a grating or popping sensation when hyperfl exing his hip. Magnetic resonance imaging (MRI) and x-ray studies in 2004 were interpreted as pigmented villonodular synovitis (PVNS) involving the right hip with extraarticular extension into the pelvis (Figure 1). An open synovectomy was performed in May 2004 through a lateral approach to both the anterior and posterior aspects of the hip. A large mass arising beneath the vastus lateralis muscle was excised (Figure 2). Th e short external rotators were deformed, and the lesion had extruded posteriorly surrounding these tendons. A capsular window was created posteriorly to leave enough attachment for circulation of the femoral head, and the PVNS material within the joint was cleaned out posteriorly and superiorly. A cyst located in the femoral neck at the subarticular surface was curetted and grafted with Norian, a bone graft substitute. Th e surgical specimen showed a tumor that demonstrated expansion of the synovium and subsynovium by sheets of mononuclear ovoid cells with moderate amounts of variably hemosiderin-laden cytoplasm (Figure 3). Scattered multinucleate giant cells were present, as were numerous mitotic fi gures. Th e tumor infi ltrated beyond the synovium to erode and penetrate adjacent bone. Stains confi rming the diagnosis of diff use PVNS, synonymously known as diff use giant cell tumor of tendon sheath, included a positive CD68, an elevated MIB-1, and a positive Prussian blue stain for iron. Tumor was present at multiple margins of resection.