PMC4898176_01
72-year-old man with giant-cell tumor of the tendon sheath. FDG PET/CT. Attenuation-corrected, maximum-intensity projection FDG PET shows intense FDG uptake within the lateral compartment of the right knee.
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His disease remained stable off therapy until April 2009, when a followup noncontrast FDG PET/CT scan revealed an intensely hypermetabolic intra-articular soft-tissue-density lesion in the left knee (SUVmax = 25 g/ml); this was thought to be highly suspicious for metastatic melanoma (Fig. 1), although no prior imaging of the knee was available to establish the chronicity of the finding.
72-year-old man with giant-cell tumor of the tendon sheath. FDG PET/CT. Bone-windowed transaxial image from the noncontrast CT component shows a solid, soft-tissue-density, intra-articular mass, centered at the synovium.
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72-year-old man with giant-cell tumor of the tendon sheath. FDG PET/CT. Soft-tissue-windowed, transaxial fused PET/CT image shows intense FDG uptake within the mass. Maximum SUV was 25 g/ml.
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Immunostaining with HMB-45 was negative, thus ruling out metastatic melanoma (Fig. 3).