Pigmented villonodular synovitis of the thoracic spine.

Pigmented villonodular synovitis (PVNS) is a proliferative lesion of the synovial membranes. Knees, hips, and other large weight-bearing joints are most commonly affected. PVNS rarely presents in the spine, in particular the thoracic segments. We present a patient with PVNS in the thoracic spine and describe its clinical presentation, radiographic findings, pathologic features, and treatment as well as providing the first comprehensive meta-analysis and review of the literature on this topic, to our knowledge. A total of 28 publications reporting 56 patients were found. The lumbar and cervical spine were most frequently involved (40% and 36% of patients, respectively) with infrequent involvement of the thoracic spine (24% of patients). PVNS affects a wide range of ages, but has a particular predilection for the thoracic spine in younger patients. The mean age in the thoracic group was 22.8years and was significantly lower than the cervical and lumbar groups (42.4 and 48.6years, respectively; p=0.0001). PVNS should be included in the differential diagnosis of osteodestructive lesions of the spine, especially because of its potential for local recurrence. The goal of treatment should be complete surgical excision. Although the pathogenesis is not clear, mechanical strain may play an important role, especially in cervical and lumbar PVNS. The association of thoracic lesions and younger age suggests that other factors, such as neoplasia, derangement of lipid metabolism, perturbations of humoral and cellular immunity, and other undefined patient factors, play a role in the development of thoracic PVNS.