Abstract: Purpose of the report: Although MRI is utilized for planning the resection of soft-tissue tumors, it is not always capable of differentiating benign from malignant lesions. The risk of local recurrence of soft-tissue sarcomas is increased when biopsies are performed before resection and by inadequate resections. PET associated with computed tomography using fluorodeoxyglucose labeled with fluorine-18 (18F-FDG PET/CT) may help differentiate between benign and malignant tumors, thus avoiding inadequate resections and making prior biopsies unnecessary. The purpose of this study was to evaluate the usefulness of 18F-FDG PET/CT in differentiating benign from malignant solid soft-tissue lesions. Materials and methods: Patients with solid lesions of the limbs or abdominal wall detected by MRI were submitted to 18F-FDG PET/CT. The maximum standardized uptake value (SUV max) cutoff was determined to differentiate malignant from benign tumors. Regardless of the 18F-FDG PET/CT results all patients underwent biopsy and surgery. Results: MRI was performed in 54 patients, and 10 patients were excluded because of purely lipomatose or cystic lesions. 18F-FDG PET/CT was performed in the remaining 44 patients. Histopathology revealed 26 (59%) benign and 18 (41%) malignant soft-tissue lesions. A significant difference in SUVmax was observed between benign and malignant soft-tissue lesions. The SUVmax cutoff of 3.0 differentiated malignant from benign lesions with 100% sensitivity, 83.3% specificity, 89.6% accuracy, 78.3% positive predictive value, and 100% negative predictive value. Conclusion: 18F-FDG PET/CT seems to be able to differentiate benign from malignant soft-tissue lesions with good accuracy and very high negative predictive value. Incorporating 18F-FDG PET/CT into the diagnostic algorithm of these patients may prevent inadequate resections and unnecessary biopsies Ver menos