Conventional and functional MR imaging of peripheral nerve sheath tumors: initial experience.
OBJECTIVE
Differentiating benign from malignant peripheral nerve sheath tumors can be very challenging using conventional MR imaging. Our aim was to test the hypothesis that conventional and functional MR imaging can accurately diagnose malignancy in patients with indeterminate peripheral nerve sheath tumors.


METHODS
This institutional review board-approved, Health Insurance Portability and Accountability Act-compliant study retrospectively reviewed 61 consecutive patients with 80 indeterminate peripheral nerve sheath tumors. Of these, 31 histologically proved peripheral nerve sheath tumors imaged with conventional (unenhanced T1, fluid-sensitive, contrast-enhanced T1-weighted sequences) and functional MR imaging (DWI/apparent diffusion coefficient mapping, dynamic contrast-enhanced MR imaging) were included. Two observers independently assessed anatomic (size, morphology, signal) and functional (ADC values, early arterial enhancement by dynamic contrast-enhanced MR) features to determine interobserver agreement. The accuracy of MR imaging for differentiating malignant from benign was also determined by receiver operating characteristic analysis.


RESULTS
Of 31 peripheral nerve sheath tumors, there were 9 malignant (9%) and 22 benign ones (81%). With anatomic sequences, average tumor diameter (6.3 ± 1.8 versus 3.9 ± 2.3 mm, P = .009), ill-defined/infiltrative margins (77% versus 32%; P = .04), and the presence of peritumoral edema (66% versus 23%, P = .01) were different for malignant peripheral nerve sheath tumors and benign peripheral nerve sheath tumors. With functional sequences, minimum ADC (0.47 ± 0.32 × 10(-3) mm(2)/s versus 1.08 ± 0.26 × 10(-3) mm(2)/s; P < .0001) and the presence of early arterial enhancement (50% versus 11%; P = .03) were different for malignant peripheral nerve sheath tumors and benign peripheral nerve sheath tumors. The minimum ADC (area under receiver operating characteristic curve was 0.89; 95% confidence interval, 0.73-0.97) and the average tumor diameter (area under the curve = 0.8; 95% CI, 0.66-0.94) were accurate in differentiating malignant peripheral nerve sheath tumors from benign peripheral nerve sheath tumors. With threshold values for minimum ADC ≤ 1.0 × 10(-3) mm(2)/s and an average diameter of ≥4.2 cm, malignancy could be diagnosed with 100% sensitivity (95% CI, 66.4%-100%).


CONCLUSIONS
Average tumor diameter and minimum ADC values are potentially important parameters that may be used to distinguish malignant peripheral nerve sheath tumors from benign peripheral nerve sheath tumors.
From The Russell H. Morgan Department of Radiology and Radiological Science (S.D., L.M.F.) demehri2001@yahoo.com.
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Demehri
Department of Neurosurgery (A.B.), Johns Hopkins University School of Medicine, Baltimore, Maryland.
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Belzberg
The Johns Hopkins Hospital Comprehensive Neurofibromatosis Center (J.B.), Department of Neurology, The Johns Hopkins Hospital, Baltimore, Maryland.
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Blakeley
From The Russell H. Morgan Department of Radiology and Radiological Science (S.D., L.M.F.).
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LM
Fayad
D000328:Adult; D000368:Aged; D019540:Area Under Curve; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018317:Nerve Sheath Neoplasms / Q000473:pathology*; D012372:ROC Curve; D012189:Retrospective Studies; D014481:United States