A SURPRISE SURGICAL FINDING: PIGMENTED VILLONODULAR SYNOVITIS

Introduction. Pigmented villonodular synovitis is a rare proliferative disorder of the synovial lining of joint, seen in just 2 cases per million. PVNS is typically a monoarticular process with two primary forms: localized and diffuse. The localized form occurs when pain and swelling is in just one area of the joint, and usually affects the small joints of the hands/feet. The diffuse form affects the entire synovial lining of the joint and typically involves the large joints, such as the knee (80% of cases). This form is significantly more common than localized PVNS and tends to be more destructive. Case presentation. We present a case of an 82-year-old male whose chief complaint was pain, swelling, and stiffness of his left knee. He had a history of smoking, cancer (CLL), and femur malunion with osteomyelitis. Physical exam revealed warmth and swelling. Xrays showed no acute fracture, but a lucent appearance in the femur along with diffuse demineralization, joint space narrowing, and osteophytes in the knee. MRI revealed degeneration of the cartilage and ACL, moderate joint effusion, grade 4 chondromalacia, and a “baker cyst.” Whole body scan was negative in the lucent area of the femur, but there was uptake in the knee. The patient was diagnosed with degenerative osteoarthritis and scheduled for knee replacement surgery. During surgery when the capsule was breached, the synovial fluid appeared as a brown semi-liquid with multiple clots. The articular surface was infiltrated with hemosiderin and the bone was osteoporotic. A radical synovectomy was performed and the decision was made to forgo the knee replacement due to bleeding, osteoporotic bone, and high risk of infection. The pathology results indicated a hyperplastic synovium with papillary projections composed of foamy cells and hemosiderin containing macrophages. Within 3 months of physical therapy, the patient had little residual pain. Deviation From the Expected. The etiology of PVNS is uncertain, although repetitive trauma, intra-articular hemorrhage, and inflammation may play a role. Synovial inflammation can invade underlining cartilage and bone resulting in significant morbidity including pain, loss of function, and eventual joint destruction if left untreated. Recurrent atraumatic hemarthrosis is the hallmark of the disorder. The classification of PVNS is still a matter of contention. Classification as a reactive granuloma would be a sound conclusion on the basis of the histology exemplary of granulation tissue. However, invasive growth and a tendency to recur indicate a potential neoplastic origin. The diagnosis is often delayed because symptoms are nonspecific. Discussion. The diagnosis of PVNS is often difficult because symptoms are non-specific and radiographs can show joint space narrowing difficult to distinguish from primary OA. CT scans demonstrate a hyperdense soft-tissue mass in the joint, which is a reflection of repeated hemorrhage and blood degradation products within the joint. On bone scan, the hypervascularity and areas of erosion may result in increased radionuclide uptake. The imaging study of choice is MRI, which demonstrates various appearances ranging from low signal to hyperintense signals, reflecting the presence of blood and its degradation products. Hemosiderin appears as low signal on T1 and T2-weighted images. The presence and amount of hemosiderin is related to the extent of mechanical trauma that the lesion undergoes. Definitive diagnosis is made by biopsy and can be confirmed by a histopathological examination, with macroscopic findings showing the presence of pigmented lipid-laden foam cells and multinucleated giant cells interspersed with hemosiderin deposits. For the diffuse form, the treatment is total synovectomy. The reoccurrence rate is as high as 46%, especially in patients with an incomplete synovectomy and extra-articular manifestations. However, when total synovectomy is combined with adjunctive radiotherapy, risk of recurrence is reduced to 10-20%. Conclusion. The exact etiology of this proliferative disease still remains unclear. More research is essential for uncovering if PVNS is to some extent neoplastic in nature, since different therapeutic approaches will be required. Grants. N/