Differentiation of peripheral nerve sheath tumors in patients with neurofibromatosis type 1 using diffusion-weighted magnetic resonance imaging

Abstract

Background. We sought to determine the value of diffusion-weighted (DW) magnetic resonance imaging (MRI) for characterization of benign and malignant peripheral nerve sheath tumors (PNSTs) in patients with neurofibromatosis type 1 (NF1). Methods. Twenty-six patients with NF1 and suspicion of malignant transformation of PNSTs were prospectively enrolled and underwent DW MRI at 3T. For a set of benign (n = 55) and malignant (n = 12) PNSTs, functional MRI parameters were derived from both biexponential intravoxel incoherent motion (diffusion coefficient D and perfusion fraction f) and monoexponential data analysis (apparent diffusion coefficients [ADCs]). A panel of morphological MRI features was evaluated using T1-and T2-weighted imaging. Mann-Whitney U-test, Fisher's exact test, and receiver operating characteristic (ROC) analyses were applied to assess the diagnostic accuracy of quantitative and qualitative MRI. Cohen's kappa was used to determine interrater reliability. Results. Malignant PNSTs demonstrated significantly lower diffusivity (P < 0.0001) compared with benign PNSTs. The perfusion fraction f was significantly higher in malignant PNSTs (P < 0.001). In ROC analysis, functional MRI parameters showed high diagnostic accuracy for differentiation of PNSTs (eg, ADC mean, 92% sensitivity with 98% specificity, AUC 0.98; D mean, 92% sensitivity with 98% specificity, AUC 0.98). By contrast, morphological imaging features had only limited sensitivity (18-94%) and specificity (18-82%) for identification of malignancy. Interrater reliability was higher for monoexponential data analysis. Conclusion. DW imaging shows better diagnostic performance than morphological features and allows accurate differentiation of benign and malignant peripheral nerve sheath tumors in NF1. Key Points 1. DWI allows sensitive and specific identification of malignancy in NF1. 2. Morphological features have limited accuracy for identifying malignant transformation. Well et al. Diffusion-weighted imaging in NF1 Neuro-Oncology Keywords diffusion-weighted imaging | intravoxel incoherent motion analysis | morphological features | neurofibromatosis type 1 | peripheral nerve sheath tumor

New Frontiers in Therapy of Peripheral Nerve Sheath Tumors in Patients With Neurofibromatosis Type 1: Latest Evidence and Clinical Implications

“…However, the morphological imaging features demonstrated limited diagnostic precision for differentiation of benign and malignant PNSTs with specificities of 18-82% and sensitivities of 18-94%. In MRI, MPNSTs present specific morphological properties including irregular shapes and margins, heterogeneity within tumor and peritumoral oedema (12)(13)(14).…”

“…Diffusion-weighted MRI (DW-MRI) without administration of intravenous contrast material improves precision compared to morphological MRI in the differentiation of malignant and benign lesions in NF1-patients. DW-MRI can be a very valuable complementary method, when borderline glucose metabolism of tumors is observed in PET imaging (12).…”

Oncological Treatment Considerations Differ across Surgical Subspecialties Treating Malignant Peripheral Nerve Sheath Tumors: An International Survey

“…Although radiological features and presenting symptoms are not specific for malignancy, some general indications should make surgeons aware of potential malignancy. Irregular shape and border, lobed aspect, cystic changes, heterogeneous structure, absence of a target sign (distinctive for neurofibromas), and peritumoral edema on MRI may indicate malignant transformation in MPNSTs [8,9,24]. Tumors larger than 5 cm or deep to the fascia definitely justify imaging and biopsy [21,23].…”

“…Recent research has shown that FDG-PET scans can be helpful in distinguishing malignant from benign lesions, differentiating MPNSTs from neurofibromas with an 80% specificity and almost 100% sensitivity [25,26], which is why an NF1 consensus does recommend performing it [22]. Others have shown that diffusion-weighted imaging sequences in MRI can differentiate malignancy with 100% specificity; however these techniques are not standard of care in many centers [24]. As neurosurgeons see neurofibromas commonly, it may explain the high proportion of neurosurgical respondents performing FDG-PET scans preoperatively.…”

Diagnostic accuracy of ultrasound‐guided core biopsy of peripheral nerve sheath tumors

“…Magnetic resonance imaging (MRI) provides reliable information about the anatomical location and size of PNSTs, but cannot reliably differentiate malignant from benign PNSTs . Improved noninvasive diagnostic performance has been found with newer techniques like Fluorodeoxyglucose‐positron emission tomography and diffusion‐weighted MRI, but the ultimate diagnosis still relies on histopathological analysis …”