Peripheral nerve sheath tumor: differentiation of malignant from benign tumors with conventional and diffusion-weighted MRI

• Published in: European radiology Vol. 31; no. 3; pp. 1548 - 1557
• Main Authors: Yun, Jae Sung, Lee, Min Hee, Lee, Seung Min, Lee, Jong Seok, Kim, Hwa Jung, Lee, Sun Joo, Chung, Hye Won, Lee, Sang Hoon, Shin, Myung Jin
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.03.2021; Springer Nature B.V
• Subjects: Benign; Cell Differentiation; Demography; Diagnosis, Differential; Diagnostic Radiology; Diffusion; Diffusion coefficient; Diffusion Magnetic Resonance Imaging; Edema; Extremities; Humans; Imaging; Internal Medicine; Interventional Radiology; Magnetic Resonance Imaging; Medicine; Medicine & Public Health; Morphology; Musculoskeletal; Nerve Sheath Neoplasms - diagnostic imaging; Neuroradiology; Peripheral nerves; Peripheral Nervous System Neoplasms - diagnosis; Radiology; Retrospective Studies; Robustness; Sensitivity and Specificity; Sheaths; Tumors; Ultrasound; Magnetic resonance imaging; Diffusion magnetic resonance imaging; Malignant peripheral nerve sheath tumor
• ISSN: 0938-7994; 1432-1084
• DOI: 10.1007/s00330-020-07234-5

Objectives To evaluate potential of conventional MRI and diffusion-weighted imaging (DWI) for differentiating malignant from benign peripheral nerve sheath tumors (PNSTs). Methods Eighty-seven cases of malignant or benign PNSTs in the trunk or extremities that underwent conventional MRI with contrast enhancement, DWI, and pathologic confirmation between Sep. 2014 and Dec. 2017 were identified. Of these, 55 tumors of uncertain nature on MRI were included. Tumor size, signal, and morphology were reviewed on conventional MRI, and apparent diffusion coefficient (ADC) values of solid enhancing portions were measured from DWI. Patient demographics, MRI features, and ADC values were compared between benign and malignant tumors, and robust imaging findings for malignant peripheral nerve sheath tumors (MPNSTs) were identified using multivariable models. Results A total of 55 uncertain tumors consisted of 18 malignant and 37 benign PNSTs. On MRI, tumor size, margin, perilesional edema, and presence of split fat, fascicular, and target signs were significantly different between groups ( p  < 0.05), as were mean and minimum ADC values ( p  = 0.002, p  < 0.0001). Most inter-reader agreement was moderate to excellent ( κ value, 0.45–1.0). The mean ADC value and absence of a split fat sign were identified as being associated with MPNSTs (odds ratios = 13.19 and 25.67 for reader 1; 49.05 and 117.91 for reader 2, respectively). The C-indices obtained by combining these two findings were 0.90 and 0.95, respectively. Conclusions Benign and malignant PNSTs showed different features on MRI and DWI. A combination of mean ADC value and absence of split fat was excellent for discriminating malignant from benign PNSTs. Key Points • It is important to distinguish between malignant peripheral nerve sheath tumors (MPNSTs) and benign peripheral nerve sheath tumors (BPNSTs) to ensure an appropriate treatment plan. • On conventional MRI and diffusion-weighted imaging (DWI), MPNSTs and BPNSTs showed significant differences in tumor size, margin, presence of perilesional edema, and absence of split fat, fascicular, and target signs. • Absence of a split fat sign and mean apparent diffusion coefficient (ADC) values were robust imaging findings distinguishing MPNSTs from BPNSTs, with a C-index of > 0.9.