The Risk of Peripheral Nerve Tumor Biopsy in Suspected Benign Etiologies

The Multimodality Management of Malignant Peripheral Nerve Sheath Tumours

Malignant peripheral nerve sheath tumours (MPNST) are aggressive sarcomas that have nerve sheath differentiation and can present at any anatomical site. They can arise from precursor neurofibroma in the context of neurofibromatosis type 1 (NF1) or as de novo and sporadic tumours in the absence of an underlying genetic predisposition. The primary therapeutic approach is most often radical surgery, with non-surgical modalities playing an important role, especially in locally advanced or metastatic cases. The aim of multimodality approaches is to optimize both local and systemic control while keeping to a minimum acute and late treatment morbidity. Advances in the understanding of the underlying biology of MPNSTs in both sporadic and NF-1-related contexts are essential for the management and implementation of novel therapeutic approaches.

Surgical Treatment and Complications of Deep-Seated Nodular Plexiform Neurofibromas Associated with Neurofibromatosis Type 1

Background: Nodular plexiform neurofibromas in individuals with neurofibromatosis type 1 often cause significant symptoms and are treated with surgical excision despite the potential risk of complications. This study aimed to clarify the surgical outcomes of deep-seated nodular plexiform neurofibromas and identify the factors associated with postoperative complications. Methods: We retrospectively reviewed patients with neurofibromatosis type 1 who underwent surgical excision for deep-seated nodular plexiform neurofibromas in our hospital from 2015 to 2021. Enucleation while preserving the nerve fascicles was attempted first, and en bloc resection, ligating the nerve origin in cases in which the parent nerve was entrapped by the tumor, making the tumor difficult to dissect, was performed. Results: In 15 patients, 24 nodular plexiform neurofibromas received surgical excision. Sixteen tumors were enucleated, and eight were en bloc resected. The symptoms of all 10 patients with preoperative symptoms resolved after surgery. Four patients developed new neurological deficits immediately after surgery, two of whom had retained neurological symptoms at the last visit, but these symptoms were mild. Conclusions: The present study demonstrates that surgical treatment of nodular plexiform neurofibromas, even deep-seated neurofibromas, is safe with a low risk of severe complications and improvement in preoperative symptoms.

Cervical Paraspinal Chordoma: A Literature Review with a Novel Case Report

Chordomas are rare malignant neoplasms, accounting for 1–4% of all primary bone tumors. Most spinal chordomas occur in the sacrococcygeal region and the base of the skull; however, 6% of chordomas are observed in the cervical spine. In these cases, the lesion is mainly located in the midline. These tumors slowly grow before becoming symptomatic and encase the surrounding vascular and nerve structures. Patients with advanced chordoma have a poor prognosis due to local recurrence with infiltration and destruction of adjacent bone and tissues. Systemic chemotherapy options have not been fully effective in these tumors, especially for recurrent chordomas. Thus, new combinations of currently available targeted molecular and biological therapies with radiotherapy have been proposed as potential treatment modalities. Here, the present paper describes the case of a 41-year-old male with a C2–C4 chordoma located paravertebrally, who underwent surgical resection with a debulking procedure for a cervical chordoma. Computed tomography angiography revealed a paraspinal mass with bone remodeling and the MRI showed a paravertebral mass penetrating to the spinal canal with a widening of the intervertebral C2–C3 foramen. Initially, the tumor was diagnosed as schwannoma based on its localization and imaging features; however, the histopathology specimen confirmed the diagnosis of chordoma. This case study highlights the effectivity of radical surgical resection as a mainstay treatment for chordomas, discusses neuroimaging, diagnosis, and the use of currently available targeted therapies and forthcoming treatment strategies, as alternative treatment options for chordoma.

Clinical results after surgical resection of benign solitary schwannomas: A review of 150 cases

INTRODUCTION

Peripheral nerve schwannomas are the most common nerve tumors. While they are efficiently treated with surgery, the risk of neurological complications, especially sensory deficits, remains debated.

HYPOTHESIS

We postulate that rates of post-operative sensory deficits in peripheral schwannoma surgery are low and are not increased in schwannomas of the hand, in which preservation of discriminative tact is of prime functional importance.

MATERIALS AND METHODS

A retrospective multicenter study was carried out on 150 patients with an isolated peripheral schwannoma operated between 2002 and 2018, including 11 patients with schwannomas of the hand. All cases were reviewed preoperatively and postoperatively with a detailed exam of the neurological status.

RESULTS

Most schwannomas were located in the lower limbs (58%). The two main affected trunks were the posterior tibial nerve in the lower limb and the median nerve in the upper limb. The average preoperative tumor volume measured on MRI was 2.93 cm³ [0.11 cm³-25 cm³]. The most common preoperative symptoms were paresthesia (77.1%) and pseudo-Tinel sign (55.7%). Less frequently, pain (50.3%) and hypoesthesia (18.1%) were observed. On the other hand, preoperative neurological motor manifestations remained exceptional (3.3%). The rates of new post-operative motor deficits, paresthesias, and sensory deficits were 4.6%, 10.9% and 8% respectively and were not increased in schwannomas of the collateral nerves of the hand.

CONCLUSION

Surgical resection is a safe procedure for peripheral nerve schwannoma treatment with satisfying functional results and an acceptable risk of nerve injury, especially for sensory function.

LEVEL OF PROOF

D; Multicenter retrospective study.

Malignant Peripheral Nerve Sheath Tumors-A Comprehensive Review of Pathophysiology, Diagnosis, and Multidisciplinary Management

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive soft tissue sarcomas (STS) with nerve sheath differentiation and a tendency to metastasize. Although occurring at an incidence of 0.001% in the general population, they are relatively common in individuals with neurofibromatosis type 1 (NF1), for whom the lifetime risk approaches 10%. The staging of MPNSTs is complicated and requires close multi-disciplinary collaboration. Their primary management is most often surgical in nature, with non-surgical modalities playing a supportive, necessary role, particularly in metastatic, invasive, or widespread disease. We, therefore, sought to provide a comprehensive review of the relevant literature describing the characteristics of these tumors, their pathophysiology and risk factors, their diagnosis, and their multi-disciplinary treatment. A close partnership between surgical and medical oncologists is therefore necessary. Advances in the molecular characterization of these tumors have also begun to allow the integration of targeted RAS/RAF/MEK/ERK pathway inhibitors into MPNST management.

Analysis of the effect of intraoperative neuromonitoring during resection of benign nerve sheath tumors on gross-total resection and neurological complications

OBJECTIVE

The aim of this study was to examine the role of intraoperative neuromonitoring (IONM) during resection of benign peripheral nerve sheath tumors in achieving gross-total resection (GTR) and in reducing postoperative neurological complications.

METHODS

Data from consecutive adult patients who underwent resection of a benign peripheral nerve sheath tumor at 7 participating institutions were combined. Propensity score matching was used to balance covariates. The primary outcomes of interest were the association between IONM and GTR and the association of IONM and the development of a permanent postoperative neurological complication. The secondary outcomes of interest were the association between IONM and GTR and the association between IONM and the development of a permanent postoperative neurological complication in the subgroup of patients with tumors involving a motor or mixed nerve. Univariate and multivariate logistic regression were then performed on the propensity score-matched samples to assess the ability of the independent variables to predict the outcomes of interest.

RESULTS

A total of 337 patients who underwent resection of benign nerve sheath tumors were included. In multivariate analysis, the use of IONM (OR 0.460, 95% CI 0.199-0.978; p = 0.047) was a significant negative predictor of GTR, whereas none of the variables, including IONM, were associated with the occurrence of a permanent postoperative neurological complication. Within the subgroup of motor/mixed nerve tumors, in the multivariate analysis, IONM (OR 0.263, 95% CI 0.096-0.723; p = 0.010) was a significant negative predictor of a GTR, whereas IONM (OR 3.800, 95% CI 1.925-7.502; p < 0.001) was a significant positive predictor of a permanent postoperative motor deficit.

CONCLUSIONS

Overall, 12% of the cohort had a permanent neurological complication, with new or worsened paresthesias most common, followed by pain and then weakness. The authors found that formal IONM was associated with a reduced likelihood of GTR and had no association with neurological complications. The authors believe that these data argue against IONM being considered standard of care but do not believe that these data should be used to universally argue against IONM during resection of benign nerve sheath tumors.

Machine Learning Approach to Differentiation of Peripheral Schwannomas and Neurofibromas: A Multi-Center Study

BACKGROUND

Non-invasive differentiation between schwannomas and neurofibromas is important for appropriate management, preoperative counseling, and surgical planning, but has proven difficult using conventional imaging. The objective of this study was to develop and evaluate machine learning approaches for differentiating peripheral schwannomas from neurofibromas.

METHODS

We assembled a cohort of schwannomas and neurofibromas from 3 independent institutions and extracted high-dimensional radiomic features from gadolinium-enhanced, T1-weighted MRI using the PyRadiomics package on Quantitative Imaging Feature Pipeline. Age, sex, neurogenetic syndrome, spontaneous pain, and motor deficit were recorded. We evaluated the performance of 6 radiomics-based classifier models with and without clinical features and compared model performance against human expert evaluators.

RESULTS

107 schwannomas and 59 neurofibroma were included. The primary models included both clinical and imaging data. The accuracy of the human evaluators (0.765) did not significantly exceed the no-information rate (NIR), whereas the Support Vector Machine (0.929), Logistic Regression (0.929), and Random Forest (0.905) classifiers exceeded the NIR. Using the method of DeLong, the AUC for the Logistic Regression (AUC=0.923) and K Nearest Neighbor (AUC=0.923) classifiers was significantly greater than the human evaluators (AUC=0.766; p = 0.041).

CONCLUSIONS

The radiomics-based classifiers developed here proved to be more accurate and had a higher AUC on the ROC curve than expert human evaluators. This demonstrates that radiomics using routine MRI sequences and clinical features can aid in differentiation of peripheral schwannomas and neurofibromas.

Machine-Learning Approach to Differentiation of Benign and Malignant Peripheral Nerve Sheath Tumors: A Multicenter Study

BACKGROUND

Clinicoradiologic differentiation between benign and malignant peripheral nerve sheath tumors (PNSTs) has important management implications.

OBJECTIVE

To develop and evaluate machine-learning approaches to differentiate benign from malignant PNSTs.

METHODS

We identified PNSTs treated at 3 institutions and extracted high-dimensional radiomics features from gadolinium-enhanced, T1-weighted magnetic resonance imaging (MRI) sequences. Training and test sets were selected randomly in a 70:30 ratio. A total of 900 image features were automatically extracted using the PyRadiomics package from Quantitative Imaging Feature Pipeline. Clinical data including age, sex, neurogenetic syndrome presence, spontaneous pain, and motor deficit were also incorporated. Features were selected using sparse regression analysis and retained features were further refined by gradient boost modeling to optimize the area under the curve (AUC) for diagnosis. We evaluated the performance of radiomics-based classifiers with and without clinical features and compared performance against human readers.

RESULTS

A total of 95 malignant and 171 benign PNSTs were included. The final classifier model included 21 imaging and clinical features. Sensitivity, specificity, and AUC of 0.676, 0.882, and 0.845, respectively, were achieved on the test set. Using imaging and clinical features, human experts collectively achieved sensitivity, specificity, and AUC of 0.786, 0.431, and 0.624, respectively. The AUC of the classifier was statistically better than expert humans (P = .002). Expert humans were not statistically better than the no-information rate, whereas the classifier was (P = .001).

CONCLUSION

Radiomics-based machine learning using routine MRI sequences and clinical features can aid in evaluation of PNSTs. Further improvement may be achieved by incorporating additional imaging sequences and clinical variables into future models.

Surgical Management of Symptomatic Lumbar, Sacral, and Lumbosacral Plexus Tumors: a Peripheral Nerve Unit Experience

OBJECTIVE

Data concerning the surgical treatment of lumbosacral plexus tumors (LSPTs) is scarce. This study aims to present our experience with a series of 19 patients surgically treated for symptomatic LSPTs at our institution.

METHODS

This is a retrospective study of 19 patients surgically treated for symptomatic LSPTs from 2011 to 2019. Clinical data were retrieved from medical records and consisted of age, gender, clinical presentation, location of the lesion, surgical approach, final histopathologic diagnosis, follow-up time, outcomes, and complications.

RESULTS

Nineteen surgical procedures were conducted. Thirteen patients were female and six, male. The median age of patients was 45 years (range 20 to 63 years). No patients harbored genetic syndromes. Surgical treatment appears to be correlated to the reduction of pain in patients with peripheral nerve sheath tumors (PNSTs), as assessed by visual analog scale (VAS). Sixteen patients did not present with new-onset deficits during follow-up (84.2%), two of whom recovered from their preoperative deficit. Four patients presented with postoperative weakness. The histopathological diagnoses were 11 schwannomas, four neurofibromas, three metastases, and one lymphoma.

CONCLUSIONS

LSPTs are rare. When surgical treatment is indicated, it usually requires multidisciplinary management. Surgery appears to be effective concerning the reduction of pain in PNSTs and may also recover neurological deficits. Iatrogenic neurological deficits are an evident risk, such that intraoperative multimodal monitoring should always be performed if available. In lesions involving the sacral plexus, we found it to be indispensable.

A Bayesian approach for diagnostic accuracy of malignant peripheral nerve sheath tumors: a systematic review and meta-analysis

Background

Malignant peripheral nerve sheath tumors (MPNST) carry a dismal prognosis and require early detection and complete resection. However, MPNSTs are prone to sampling errors and biopsies or resections are cumbersome and possibly damaging in benign peripheral nerve sheath tumor (BPNST). This study aimed to systematically review and quantify the diagnostic accuracy of noninvasive tests for distinguishing MPNST from BPNST.

Methods

Studies on accuracy of MRI, FDG-PET (fluorodeoxyglucose positron emission tomography), and liquid biopsies were identified in PubMed and Embase from 2000 to 2019. Pooled accuracies were calculated using Bayesian bivariate meta-analyses. Individual level-patient data were analyzed for ideal maximum standardized uptake value (SUV_max) threshold on FDG-PET.

Results

Forty-three studies were selected for qualitative synthesis including data on 1875 patients and 2939 lesions. Thirty-five studies were included for meta-analyses. For MRI, the absence of target sign showed highest sensitivity (0.99, 95% CI: 0.94-1.00); ill-defined margins (0.94, 95% CI: 0.88-0.98); and perilesional edema (0.95, 95% CI: 0.83-1.00) showed highest specificity. For FDG-PET, SUV_max and tumor-to-liver ratio show similar accuracy; sensitivity 0.94, 95% CI: 0.91-0.97 and 0.93, 95% CI: 0.87-0.97, respectively, specificity 0.81, 95% CI: 0.76-0.87 and 0.79, 95% CI: 0.70-0.86, respectively. SUV_max ≥3.5 yielded the best accuracy with a sensitivity of 0.99 (95% CI: 0.93-1.00) and specificity of 0.75 (95% CI: 0.56-0.90).

Conclusions

Biopsies may be omitted in the presence of a target sign and the absence of ill-defined margins or perilesional edema. Because of diverse radiological characteristics of MPNST, biopsies may still commonly be required. In neurofibromatosis type 1, FDG-PET scans may further reduce biopsies. Ideal SUV_max threshold is ≥3.5.

Percutaneous image-guided biopsy in malignant peripheral nerve sheath tumors

BACKGROUND

The decision to biopsy a peripheral nerve tumor is largely based on its presumed behavior and prognosis, determined by patient history, clinical exam, and radiologic characteristics. Percutaneous image-guided biopsy is not without risk in patients with malignant peripheral nerve sheath tumors (MPNSTs); in particular, there may be concern regarding worsening neurologic function, increasing neuropathic pain, and incorrect or absent diagnosis.

METHODS

Following approval by our institutional review board, we reviewed records from 1990 to 2019 at our institution's three main sites ("our institution"). Patients with pathology-proven MPNST were selected. Further inclusion criteria included image-guided percutaneous biopsy performed at our institution, pathology report available for review, and follow-up documentation to determine post-biopsy complications.

RESULTS

Three hundred thirty-one patients with MPNST were reviewed. In total, 73 patients undergoing image-guided percutaneous biopsies were included. Twenty-two (30.1%) had biopsy-related complications. This included ten patients with misdiagnosis (13.7%) and six patients with non-diagnostic biopsies (8.2%). Six patients had new or worsened pain that resolved with time and neuropathic pain medication (8.2%), and one patient had subjectively worsened proximal weakness (1.3%) which resolved.

CONCLUSION

We found nearly a third of patients undergoing biopsy had a biopsy-related complication. The single largest complication was the inability to obtain an accurate diagnosis (21.9%) with the first biopsy. This may lead to the need for repeat percutaneous or open biopsies, or a non-oncologic initial surgery with implications for disease-free and overall survival. Neurologic complications including exacerbation of pain or a deficit were rare and transient. It remains important that clinicians balance the potential risks and benefits based on individual patient characteristics when determining the necessity of an image-guided percutaneous biopsy.

Image-guided percutaneous biopsy of peripheral nerve tumors of indeterminate nature: risks and benefits

BACKGROUND

Usual management of peripheral nerve tumors is to avoid biopsy in those that are likely benign; the risk of biopsy outweighs the benefit of definitive tissue diagnosis. Biopsy of presumed malignant lesions is performed widely. There is a subset of peripheral nerve tumors that are not easily categorized as benign or malignant based on the clinical and/or radiological features alone. The role of biopsy in peripheral nerve tumors of uncertain character remains controversial and the risk of biopsy (and the potential risk/benefit ratio) for these lesions is not known.

METHODS

Following approval by our institutional review board, we reviewed all notes of a single peripheral nerve surgeon from 2000 to 2018 with respect to image-guided percutaneous biopsy of nerve tumors. We divided these patients into 3 groups based on clinicoradiologic features. We determined the risk of complications and the "hit rate" for patients with peripheral nerve tumors of uncertain behavior, defined as the percentage of patients sent for percutaneous biopsy who had a malignancy on their final pathology.

RESULTS

Of 82 patients with tumors of uncertain behavior, 9 had complications, and 23 had malignant final pathology (a "hit rate" of 27.7%). Neurosurgical referral for biopsy of tumors of uncertain behavior was made in 60 patients. Twenty-two had malignant final pathology ("hit rate"= 36.7%). Non-neurosurgical referral for biopsy was made in 22 patients with tumors of uncertain behavior. Two had malignant final pathology ("hit rate"= 4.55%). There was a statistically significant difference between the "hit rate" for the two groups (p = 0.021).

CONCLUSIONS

The decision to biopsy a peripheral nerve tumor is largely based on the presumed behavior and prognosis, determined via clinicoradiologic characteristics. Patient care might be improved by delaying percutaneous biopsy of peripheral nerve lesions until after a neurosurgical evaluation.

Schwannomas of the sciatic nerve: A rare and neglected diagnosis. A review of the literature with two illustrative cases

OBJECTIVE

Schwannomas of the sciatic nerve, which is the largest nerve of the human body, are very rare accounting for ≤ 1% of all schwannomas. They often may raise confusion with other more common causes of sciatica, such as lumbar degenerative and inflammatory diseases or spinal tumors, which may often lead to a late correct diagnosis.

PATIENTS AND METHODS

We present two cases of sciatic nerve schwannomas that were recently treated at our Institution, and we review the pertinent English literature on this topic over the last 15 years, yielding twenty three cases to analyze.

RESULTS

Even if sciatic nerve schwannomas are a rare occurrence, a thorough clinical and radiological evaluation of the sciatic nerve should be considered whenever a sciatic pain is not otherwise explained. A positive Tinel sign and a palpable mass along the course of the sciatic nerve may be strong clues to achieve the diagnosis. Combined morphological and advanced functional MRI imaging may help to differentiate benign from malignant peripheral nerve sheath tumors, avoiding unnecessary preoperative biopsy.

CONCLUSIONS

A standard microsurgical technique guided by ultrasound and neurophysiologic monitoring, allows in most of the cases a safe removal of the tumor and very satisfactory post-operative results for the patients.

Treatment of malignant peripheral nerve sheath tumors in pediatric NF1 disease

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNSTs) are rare yet highly aggressive soft tissue sarcomas. Children with neurofibromatosis type 1 (NF1) have a 10% lifetime risk for development of MPNST. Prognosis remains poor and survival seems worse for NF1 patients.

METHODS

This narrative review highlights current practices and pitfalls in the management of MPNST in pediatric NF1 patients.

RESULTS

Preoperative diagnostics can be challenging, but PET scans have shown to be useful tools. More recently, functional MRI holds promise as well. Surgery remains the mainstay treatment for these patients, but careful planning is needed to minimize postoperative morbidity. Functional reconstructions can play a role in improving functional status. Radiotherapy can be administered to enhance local control in selected cases, but care should be taken to minimize radiation effects as well as reduce the risk of secondary malignancies. The exact role of chemotherapy has yet to be determined. Reports on the efficacy of chemotherapy vary as some report lower effects in NF1 populations. Promisingly, survival seems to ameliorate in the last few decades and response rates of chemotherapy may increase in NF1 populations when administering it as part of standard of care. However, in metastasized disease, response rates remain poor. New systemic therapies are therefore desperately warranted and multiple trials are currently investigating the role of drugs. Targeted drugs are nevertheless not yet included in first line treatment.

CONCLUSION

Both research and clinical efforts benefit from multidisciplinary approaches with international collaborations in this rare malignancy.