The aim of this study was to compare the diagnostic performance of 18F-fluorodeoxyglucose (FDG) PET/CT and whole-body MRI for the detection of malignant peripheral nerve sheath tumors (MPNSTs) in patients with neurofibromatosis type 1, and to evaluate a panel of imaging-based criteria serving that purpose.
Thirty-one patients were examined by whole-body MRI and 18F-FDG PET/CT. A panel of imaging-based criteria including tumor region, size, shape, margin definition, contrast enhancement, heterogeneity before and after contrast, intratumoral lobulation, target sign, and mean and maximum standardized uptake values (SUVs) were evaluated. A SUVmax cut-off value of 3.5 was used for lesion analysis. Histopathologic evaluation and/or clinical follow-up served as the reference standard.
18F-FDG PET/CT had a sensitivity of 100%, whereas MRI had a sensitivity of 66.7%. On PET/CT, tumor size (P < 0.005), SUVmax (P < 0.0001), SUVmean (P < 0.0001), and tracer uptake heterogeneity (P = 0.002) were significantly associated with MPNSTs. On MRI, intratumoral lobulation (P < 0.02), ill-defined margins (P = 0.007), and irregular enhancement on T1-weighted imaging (P < 0.001) were significantly associated with MPNSTs.
Both PET/CT and whole-body MRI may distinguish benign and malignant PNSTs, but PET/CT has higher sensitivity for that purpose. Imaging-based criteria for identification of MPNSTs on both modalities were identified. False-positive results, requiring biopsy or clinical follow-up, may be reduced by using a combination of MRI and PET derived markers, but only at the price of reduced sensitivity.
From the *Department of Diagnostic and Interventional Radiology, †Department of Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Hamburg; and ‡Department of Nuclear Medicine, Universitätsmedizin Charité Berlin, Berlin; §Institute of Neuropathology, ¶Department of Oral and Maxillofacial Surgery, and ∥Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Received for publication March 18, 2012; and revision accepted June 7, 2012.
Conflicts of interest and sources of funding: none declared.
Reprints: Thorsten Derlin, MD, Department of Diagnostic and Interventional Radiology, University Hospital Hamburg-Eppendorf, Martinistr. 52, DE 20246 Hamburg, Germany. E-mail: firstname.lastname@example.org.