Pigmented villonodular synovitis and pigmented villonodular bursitis: Imaging findings and review of the literature

Learning Objectives: To review the pathologic basis of pigmented villonodular synovitis (PVNS) and bursitis (PVNB). To describe the imaging appearances of PVNS and PVNB using conventional radiography (CR), ultrasonography (US) and magnetic resonance (MR) imaging. Background: PVNS is a rare proliferative disorder of the synovial membrane that may occur diffusely or focally. PVNB is the same pathology with the difference that the synovial involvement occurs in an extra-articular site, as a bursa. They primarily involve young adults and appear with non-specific symptoms (swelling, pain) which mimic other pathologies, including traumatic injuries, thus often delaying the correct diagnosis. Imaging Findings: CR imaging may appear normal or reveal a non-specific soft-tissue mass; visible calcifications are rare. US imaging may detect joint effusion, complex heterogeneous echogenic masses, and a markedly thickened hypoechoic synovium. MR imaging may demonstrate the disease extension (particularly in case of bursal involvement) to best advantage, and the predominant low signal intensity of the lesions on T2-weighted images is a characteristic sign of the disease. Moreover, the “blooming artifact” seen on gradient-echo images, caused by the magnetic susceptibility artifact from hemosiderin deposition in these lesions, is a nearly pathognomonic sign of this disease. Conclusion: Detection of disease location and extension are important both for diagnosis and to guide treatment. MR is the best diagnostic imaging tool to identify the presence of haemosiderin deposition within the nodules, thus characterizing the lesion. This information is crucial to guide treatment and to achieve complete surgical resection.