本文報告一例在三年前曾經患有脂肉瘤（liposarcoma），同時亦接受過手術及放射線治療的23歲男性病人，在定期追蹤的檢查當中，發現有不正常的氟-18-去氧葡萄糖（FDG）的吸收，但其他所有檢查及最後病理報告的結果皆為正常。此病例主要強調在正予造影（PET）的過程當中，必須注意在判讀上可能會造成偽陽性的陷阱。

　　　　　Fluorine-18-fluorodeoxyglucose positron emission tomographic (18F-FDG PET) imaging has been shown to be a useful and valuable method in detecting malignant soft-tissue sarcoma, identifying the grade of primary tumor and differentiating recurrent tumor from radiation necrosis and/or postoperative scar of patient with soft-tissue sarcoma after therapy. However, FDG is not a cancer-specific agent, and benign disease sometimes has been reported to cause intense uptake that is difficult to differentiate from malignant disease. We present an unusual case with increased FDG uptake mimicking local recurrence of malignancy in the scar tissue of a patient of myxoid liposarcoma in the right thigh after wide excision with rotational flap reconstruction and postoperative radiotherapy about 3 years ago.