A woman was referred for fluorodeoxyglucose positron emission tomography for the staging of a malignant melanoma. Although no signs of metastatic melanoma were evident on the whole-body scan, focally increased uptake within the femoral metaphysis was noted. Radiographic and magnetic resonance examinations revealed an enchondroma as the cause of the increased uptake. Histopathologic verification was obtained. The final diagnosis was actively proliferating enchondroma. A grade I chondrosarcoma could be ruled out. Enchondromas may be responsible for focally increased FDG uptake in bone lesions and must be considered when positron emission tomographic scans obtained with FDG are evaluated in cancer staging.
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