Fascicle Sparing Capsular Resections of Atypical Neurofibromas in Neurofibromatosis 1

INTRODUCTION: Neurofibromatosis type 1 (NF1) patients are predisposed to neurofibromas (NF), which can progress to premalignant atypical neurofibromas (ANF) and malignant peripheral nerve sheath tumors (MPNST). Subtotal resection of ANF may prevent metastases and deaths, but local recurrences require reoperation. Here, we assess the surgical morbidity associated with gross total, extracapsular resection of targeted ANF nodules identified via serial volumetric magnetic resonance imaging (MRI) and 18F-FDG-PET imaging. METHODS: We retrospectively analyzed the clinical outcomes of 11 NF1 patients following 16 NF surgical resections of 21 tumors at the NIH Clinical Center between 2008 and 2018. Preoperative volumetric growth rates and 18F-FDG-PET SUVMAX of the target lesions were measured and assessed in tandem with postoperative complications, histopathological classification of the resected tumors, and surgical margins through Dunnett's multiple comparison tests and t-tests. RESULTS: Preoperatively, 13 of the 14 (93%) sets of serial preoperative MRI scans showed rapid growth (= 20% increase in volume per year), and 10 of the 11 (91%) 18F-FDG-PET scans indicated increased positron emission tomography (PET) avidity (median SUVMax = 6.45). Gross total, extracapsular resections of the targeted neurofibroma nodules were annotated by the surgeon in all 16 (100%) surgeries, and most surgeries (n = 14, 88%) resulted in no persistent postoperative parent nerve-related complications. SUVMax was significantly greater in the ANF (6.51 ± 0.83, P = .0042) and low grade MPNST (13.8, P = .0001) strata than in the benign NF (1.9) stratum. To date, none of the resected NF have recurred. CONCLUSION: This study confirms that the combination of increased 18F-FDG-PET SUVMax, rapid growth, and pain can serve as reliable indicators of atypical transformation and the need for surgical intervention. We also demonstrate the ability to achieve safe, fascicle-sparing gross total, extracapsular resection of ANF using intraoperative nerve stimulation, histological verification, and continued monitoring for tumor recurrence.