• Hiroshi Koike, Yoshihiro Nishida, Shinji Ito, Yoshie Shimoyama, Kunihiro Ikuta, Hiroshi Urakawa, Tomohisa Sakai, Koki Shimizu, Kan Ito, and Shiro Imagama.
• Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, Showa, Nagoya, Japan.
• World Neurosurg. 2022 Jan 1; 157: e207-e214.

ObjectiveIn patients with neurofibromatosis type 1 (NF1), it is important to accurately determine when plexiform neurofibroma (pNF) transforms to a malignant peripheral nerve sheath tumor (MPNST). The purpose of this study is to investigate the usefulness of diffusion-weighted imaging (DWI) in differentiating pNF and MPNST in NF1 patients.MethodsAmong the NF1 patients who were referred to our hospital between 1985 and 2015, 10 cases of MPNST and 19 cases of pNF were included. We evaluated features of standard magnetic resonance imaging according to the differentiation criteria of malignancy from benignancy as previously reported, apparent diffusion coefficient (ADC) value based on the DWI and the correlation between ADC value and benignancy/malignancy. ROC analysis was performed to determine the appropriate cutoff value of ADC.ResultsThere were significant differences between MPNST and pNF in the size of the tumor (P = 0.009), peripheral enhancement pattern (P = 0.002), perilesional edema-like zone (P = 0.0008), and intratumoral cystic change (P = 0.02). The mean and minimum values of ADC were significantly lower in MPNST than those in pNF (P = 0.03 and P = 0.003, respectively). When we set a cutoff value of mean ADC as 1.85 × 10-3 mm2/s, the sensitivity and specificity were 80% and 74%, respectively. The area under the curve value improved by adding the Wasa score to the mean ADC evaluation.ConclusionsADC values determined by DWI are useful in differentiating MPNST from pNF and adding ADC evaluation to standard MRI evaluation improved the diagnostic accuracy.Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.

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