Association between benign and malignant peripheral nerve sheath tumors in NF1

Association of plexiform and diffuse neurofibromas with malignant peripheral nerve sheath tumor in NF I patients: a whole-body MRI assessment

OBJECTIVE

The aim of this study is to evaluate neurofibromatosis type 1 (NF1) patients with whole-body MRI (WBMRI) to investigate the frequency of plexiform neurofibromas (pNFs), diffuse neurofibromas (dNFs), and malignant peripheral nerve sheath tumors (MPNSTs).

MATERIALS AND METHODS

In this retrospective cross-sectional study, between the years 2015 and 2023, 83 consecutive patients with known NF1 underwent a total of 110 WBMRI screenings for MPNST using a standardized institutional protocol. The lesions are categorized as discrete lesions, pNFs, dNFs, and MPNSTs. Histopathology served as the reference standard for all MPNSTs.

RESULTS

Among the 83 patients analyzed, 53 (64%) were women and 30 were men (36%) of ages 36.94±14.43 years (range, 15-66 years). Of the 83 patients, 33 have a positive family history of NF1 and positive genetic studies. Seven of 83 (8%) have only dNF, 20/83 (24%) have pNF, 28/83 (34%) have both dNF and pNF, and 28/83 (34%) have neither. Of the 83 patients, eight (9.6%) were diagnosed with nine total MPNSTs. Age range for patients with MPNSTs at time of diagnosis was 22-51, with an average age of 33.4 years. Only one MPNST (11%) developed from underlying pNF 4 years after WBMRI along the right bronchial tree. Three of eight (37.5%) patients with MPNST died within 5 years of pathologic diagnosis.

CONCLUSION

This study suggests the absence of a predisposition for development of MPNST from pNFs and dNFs in the setting of NF1. As such, these lesions may not need special surveillance compared to discrete peripheral nerve sheath tumors.

The Lack of Ad Hoc Neuropsychological Assessment in Adults with Neurofibromatosis: A Systematic Review

Background: Neurofibromatosis Type 1 (NF1) is a genetic autosomal dominant disorder that affects both the central and peripheral nervous systems. Children and adolescents with NF1 commonly experience neuropsychological, motor, and behavioral deficits. The cognitive profile hallmark of this disorder includes visuospatial and executive function impairments. These cognitive disorders may persist into adulthood. This study aims to analyze previous research studies that have described cognitive dysfunctions in adults with NF1. The purpose of this analysis is to review the neuropsychological and psychological assessment methods used. Methods: A total of 327 articles were identified based on the search terms in their titles and abstracts. The evaluation was conducted by scrutinizing each article's title, abstract, and text. Results: Only 16 articles were found to be eligible for inclusion based on the pre-defined criteria. The selected studies primarily focus on the development of diagnostic protocols for individuals with NF1. Conclusions: The management of NF1 disease requires a multidisciplinary approach to address symptoms, preserve neurological functions, and ensure the best possible quality of life. However, cognitive impairment can negatively affect psychological well-being. This study suggested that cognitive functions in NF1 patients were not tested using specific measures, but rather were evaluated through intelligence scales. Additionally, the findings revealed that there is no standardized neuropsychological assessment for adults with NF1. To address this gap, it would be helpful to create a specific neuropsychological battery to study cognitive function in NF1 patients during clinical studies. This battery could also serve as a tool to design models for cognitive rehabilitation by using reliable and sensitive measures of cognitive outcomes.

Whole-Body Positron Emission Tomography with 18F-Fluorodeoxyglucose/Magnetic Resonance Imaging as a Screening Tool for the Detection of Malignant Transformation in Individuals with Neurofibromatosis Type 1

Malignant peripheral nerve sheath tumors (MPNSTs) are the leading cause of death in patients with neurofibromatosis type 1. They can result from premalignant neurofibromas, including neurofibromas with atypia and atypical neurofibromatous neoplasms of uncertain biologic potential. Some phenotypic characteristics have been described as associated with their development. The aim of this study was to outline our use of whole-body positron emission tomography with 18F-fluorodeoxyglucose/magnetic resonance imaging in adults with neurofibromatosis type 1, especially in the screening of asymptomatic individuals with a higher risk of developing an MPNST, and to study its impact on neurofibroma classification (malignant vs premalignant) and MPNST staging over time. Individuals with neurofibromatosis type 1 who underwent a positron emission tomography with 18F-fluorodeoxyglucose/magnetic resonance imaging between 2017 and 2021 were included, analyzing separately the screened population. Maximum standard uptake value and diffusion-weighted imaging were assessed. Biopsy/surgery confirmed the diagnosis. In all, 345 positron emission tomography with 18F-fluorodeoxyglucose/magnetic resonance imaging were performed in 241 patients, including 149 asymptomatic (62%) but at-risk patients. Eight MPNSTs in 8 screened individuals (5%), 6 neurofibromas with atypia in 4 individuals (3%), and 29 atypical neurofibromatous neoplasms of uncertain biologic potential in 23 individuals (15%) were diagnosed. Over time, the proportion of grade 3 MPNST and the malignant/premalignant ratio in screened individuals significantly decreased (P = .03 and P < .001, respectively). This study emphasizes the diagnostic and screening performances of whole-body positron emission tomography with 18F-fluorodeoxyglucose/magnetic resonance imaging in adults with neurofibromatosis type 1.

Droplet Digital PCR for Fast and Accurate Characterization of NF1 Locus Deletions: Confirmation of the Predominant Maternal Origin of Type-1 Deletions

Neurofibromatosis type-1 is a genetic disorder caused by loss-of-function variants in the tumor-suppressor NF1. Approximately 4% to 11% of neurofibromatosis type-1 patients have a NF1 locus complete deletion resulting from nonallelic homologous recombination between low copy repeats. Codeleted genes probably account for the more severe phenotype observed in NF1-deleted patients. This genotype-phenotype correlation highlights the need for a detailed molecular description. A droplet digital PCR (ddPCR) set along the NF1 locus was designed to delimitate the three recurrent NF1 deletion breakpoints. The ddPCR was tested in 121 samples from nonrelated NF1-deleted patients. Classification based on ddPCR versus multiplex ligation-dependent probe amplification (MLPA) was compared. In addition, microsatellites were analyzed to identify parental origin of deletions. ddPCR identified 77 type-1 (64%), 20 type-2 (16%), 7 type-3 (6%), and 17 atypical deletions (14%). The results were comparable with MLPA, except for three atypical deletions misclassified as type-2 using MLPA, for which the SUZ12 gene was not deleted. A significant maternal bias (25 of 30) in the origin of deletions was identified. This study proposes a fast and efficient ddPCR quantification to allow fine NF1 deletion classification. It indicates that ddPCR can be implemented easily into routine diagnosis to complement the techniques dedicated to NF1 point variant identification. This new tool may help unravel the genetic basis conditioning phenotypic variability in NF1-deleted patients and offer tailored genetic counseling.

Schwann cells modulate nociception in neurofibromatosis 1

Pain of unknown etiology is frequent in individuals with the tumor predisposition syndrome neurofibromatosis 1 (NF1), even when tumors are absent. Nerve Schwann cells (SCs) were recently shown to play roles in nociceptive processing, and we find that chemogenetic activation of SCs is sufficient to induce afferent and behavioral mechanical hypersensitivity in wild-type mice. In mouse models, animals showed afferent and behavioral hypersensitivity when SCs, but not neurons, lacked Nf1. Importantly, hypersensitivity corresponded with SC-specific upregulation of mRNA encoding glial cell line-derived neurotrophic factor (GDNF), independently of the presence of tumors. Neuropathic pain-like behaviors in the NF1 mice were inhibited by either chemogenetic silencing of SC calcium or by systemic delivery of GDNF-targeting antibodies. Together, these findings suggest that alterations in SCs directly modulate mechanical pain and suggest cell-specific treatment strategies to ameliorate pain in individuals with NF1.

Identification of potential common genetic modifiers of neurofibromas: a genome-wide association study in 1333 patients with neurofibromatosis type 1

BACKGROUND

Neurofibromatosis type 1 (NF1) is characterized by the highly variable and unpredictable development of benign peripheral nerve sheath tumours: cutaneous (cNFs), subcutaneous (scNFs) and plexiform (pNFs) neurofibromas.

OBJECTIVES

To identify neurofibroma modifier genes, in order to develop a database of patients with NF1.

METHODS

All patients were phenotypically evaluated by a medical practitioner using a standardized questionnaire and the causal NF1 variant identified. We enrolled 1333 patients with NF1 who were genotyped for > 7 million common variants.

RESULTS

A genome-wide association case-only study identified a significant association with 9q21.33 in the pNF phenotype in the discovery cohort. Twelve, three and four regions suggestive of association at the P ≤ 1 × 10-6 threshold were identified for pNFs, cNFs and scNFs, respectively. Evidence of replication was observed for 4, 2 and 6 loci, including 168 candidate modifier protein-coding genes. Among the candidate modifier genes, some were implicated in the RAS-mitogen-activated protein kinase pathway, cell-cycle control and myelination. Using an original CRISPR/Cas9-based functional assay, we confirmed GAS1 and SPRED2 as pNF and scNF candidate modifiers, as their inactivation specifically affected NF1-mutant Schwann cell growth.

CONCLUSIONS

Our study may shed new light on the pathogenesis of NF1-associated neurofibromas and will, hopefully, contribute to the development of personalized care for patients with this deleterious and life-threatening condition.

Distinct Transcriptional Profiles in the Different Phenotypes of Neurofibroma from the Same Subject with Neurofibromatosis 1

Neurofibromatosis 1 is a prevalent hereditary neurocutaneous disorder. Among the clinical phenotypes of neurofibromatosis 1, cutaneous neurofibroma (cNF) and plexiform neurofibroma (pNF) have distinct clinical manifestations, and pNF should be closely monitored owing to its malignant potential. However, the detailed distinct features of neurofibromatosis 1 phenotypes remain unknown. To determine whether the transcriptional features and microenvironment of cNF and pNF differ, single-cell RNA sequencing was performed on isolated cNF and pNF cells from the same patient. Six cNF and five pNF specimens from different subjects were also immunohistochemically analyzed. Our findings revealed that cNF and pNF had distinct transcriptional profiles even within the same subject. pNF is enriched in Schwann cells with characteristics similar to those of their malignant counterpart, fibroblasts, with a cancer-associated fibroblast-like phenotype, angiogenic endothelial cells, and M2-like macrophages, whereas cNF is enriched in CD8 T cells with tissue residency markers. The results of immunohistochemical analyses performed on different subjects agreed with those of single-cell RNA sequencing. This study found that cNF and pNF, the different neurofibromatosis phenotypes in neurofibromatosis 1, from the same subject are transcriptionally distinct in terms of the cell types involved, including T cells.

Discrimination of benign, atypical, and malignant peripheral nerve sheath tumors in neurofibromatosis type 1 using diffusion-weighted MRI

Background

Neurofibromatosis type 1 (NF1) is associated with the development of benign (BPNST) and malignant (MPNST) peripheral nerve sheath tumors. Recently described atypical neurofibromas (ANF) are considered pre-malignant precursor lesions to MPNSTs. Previous studies indicate that diffusion-weighted magnetic resonance imaging (DW-MRI) can reliably discriminate MPNSTs from BPNSTs. We therefore investigated the diagnostic accuracy of DW-MRI for the discrimination of benign, atypical, and malignant peripheral nerve sheath tumors.

Methods

In this prospective explorative single-center phase II diagnostic study, 44 NF1 patients (23 male; 30.1 ± 11.8 years) underwent DW-MRI (b-values 0-800 s/mm²) at 3T. Two radiologists independently assessed mean and minimum apparent diffusion coefficients (ADCmean/min) in areas of largest tumor diameters and ADCdark in areas of lowest signal intensity by manual contouring of the tumor margins of 60 BPNSTs, 13 ANFs, and 21 MPNSTs. Follow-up of ≥ 24 months (BPNSTs) or histopathological evaluation (ANFs + MPNSTs) served as diagnostic reference standard. Diagnostic ADC-based cut-off values for discrimination of the three tumor groups were chosen to yield the highest possible specificity while maintaining a clinically acceptable sensitivity.

Results

ADC values of pre-malignant ANFs clustered between BPNSTs and MPNSTs. Best BPNST vs. ANF + MPNST discrimination was obtained using ADCdark at a cut-off value of 1.6 × 10-3 mm2/s (85.3% sensitivity, 93.3% specificity), corresponding to an AUC of 94.3% (95% confidence interval: 85.2-98.0). Regarding BPNST + ANF vs. MPNST, best discrimination was obtained using an ADCdark cut-off value of 1.4 × 10-3 mm2/s (83.3% sensitivity, 94.5% specificity).

Conclusions

DW-MRI using ADCdark allows specific and noninvasive discrimination of benign, atypical, and malignant nerve sheath tumors in NF1.

Surgical management of craniospinal axis malignant peripheral nerve sheath tumors: a single-institution experience and literature review

BACKGROUND

Malignant peripheral nerve sheath tumor (MPNST) is an exceedingly rare and aggressive tumor, with limited literature on its management. Herein, we present our series of surgically managed craniospinal MPNSTs, analyze their outcomes, and review the literature.

METHODS

We retrospectively reviewed surgically managed primary craniospinal MPNSTs treated at our institution between January 2005 and May 2023. Patient demographics, tumor features, and treatment outcomes were assessed. Neurological function was quantified using the Frankel grade and Karnofsky performance scores. Descriptive statistics, rank-sum tests, and Kaplan-Meier survival analyses were performed.

RESULTS

Eight patients satisfied the inclusion criteria (4 male, 4 female). The median age at presentation was 38 years (range 15-67). Most tumors were localized to the spine (75%), and 3 patients had neurofibromatosis type 1. The most common presenting symptoms were paresthesia (50%) and visual changes (13%). The median tumor size was 3 cm, and most tumors were oval-shaped (50%) with well-defined borders (75%). Six tumors were high grade (75%), and gross total resection was achieved in 5 patients, with subtotal resection in the remaining 3 patients. Postoperative radiotherapy and chemotherapy were performed in 6 (75%) and 4 (50%) cases, respectively. Local recurrence occurred in 5 (63%) cases, and distant metastases occurred in 2 (25%). The median overall survival was 26.7 months. Five (63%) patients died due to recurrence.

CONCLUSIONS

Primary craniospinal MPNSTs are rare and have an aggressive clinical course. Early diagnosis and treatment are essential for managing these tumors. In this single-center study with a small cohort, maximal resection, low-grade pathology, young age (< 30), and adjuvant radiotherapy were associated with improved survival.

Perinatal folate levels do not influence tumor latency or multiplicity in a model of NF1 associated plexiform-like neurofibromas

OBJECTIVE

In epidemiological and experimental research, high folic acid intake has been demonstrated to accelerate tumor development among populations with genetic and/or molecular susceptibility to cancer. Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder predisposing affected individuals to tumorigenesis, including benign plexiform neurofibromas; however, understanding of factors associated with tumor risk in NF1 patients is limited. Therefore, we investigated whether pregestational folic acid intake modified plexiform-like peripheral nerve sheath tumor risk in a transgenic NF1 murine model.

RESULTS

We observed no significant differences in overall survival according to folate group. Relative to controls (180 days), median survival did not statistically differ in deficient (174 days, P = 0.56) or supplemented (177 days, P = 0.13) folate groups. Dietary folate intake was positively associated with RBC folate levels at weaning, (P = 0.023, 0.0096, and 0.0006 for deficient vs. control, control vs. supplemented, and deficient vs. supplemented groups, respectively). Dorsal root ganglia (DRG), brachial plexi, and sciatic nerves were assessed according to folate group. Mice in the folate deficient group had significantly more enlarged DRG relative to controls (P = 0.044), but no other groups statistically differed. No significant differences for brachial plexi or sciatic nerve enlargement were observed according to folate status.

Parent perspectives on disclosing a pediatric neurofibromatosis type 1 diagnosis

Neurofibromatosis 1 (NF1) is a common genetic disorder typically diagnosed in childhood and characterized by cutaneous findings, nerve sheath tumors, skeletal abnormalities, malignancies, and developmental differences. Due to its variability, NF1 is an unpredictable condition that parents have concerns about discussing with their children. While there are publications addressing the disclosure of genetic conditions in general, no NF1-specific disclosure literature exists. To fill this gap, this mixed methods study sought to evaluate the concerns, barriers, failures, or successes parents or guardians have experienced when they have or have not chosen to tell their child(ren) about an NF1 diagnosis. Parents of children between ages 0 and 17 with a diagnosis of NF1 completed a survey and some parents were selected for an interview invitation. A total of 258 surveys were completed, and 20 parents were interviewed. Interview transcripts were categorized into disclosure and non-disclosure groups. Themes were organized into five categories based on interview questions: disclosure concerns, factors affecting disclosure/non-disclosure, approaches to disclosure, desired resources, and recommendations for disclosure. Sentiment analysis was performed on responses about the disclosure discussion itself. Results indicated that most parents (70.5%) disclosed the NF1 diagnosis to their child and overall felt it was a positive experience. Almost one-third of parents (29.5%) had not disclosed the diagnosis. A strong significance was identified between disclosure and severe presentation of NF1 (p = 0.0008). Parents in both groups shared similar concerns about discussing the diagnosis and multiple factors influenced the disclosure decision. Most parents approached disclosure as a process and emphasized the need to be honest and supportive of their child. Parents highlighted the need for more educational resources for children and guidance on how to disclose. These findings indicate that additional resources and support for parents would facilitate disclosure and the involvement of genetic counselors in the process would be beneficial.

Rare case of Malign Peripheral Nerve Sheath Tumor complicating a solitary giant neurofibroma of the thigh

INTRODUCTION AND IMPORTANCE

Malign Peripheral Nerve Sheath Tumor is rare and can occur on a solitary neurofibroma or as part of neurofibromatosis type 1. The occurrence of a giant solitary neurofibroma in the thigh is rare and its complication in MPNST is much rarer. The diagnosis is based on a combination of radiological, histological and immunohistochemical evidence.

CASE PRESENTATION

We present the case of a 55 years old woman who presented a mass of the posterior aspect of the thigh without any other abnormality on systemic examination. MRI showed a T1 hyposignal and a T2 hypersignal and the biopsy performed was in favor of a neurofibroma. After surgical resection, the histological study of the surgical specimen revealed an MPNST developing on a pre-existing neurofibroma. After 5 months, the patient had moderate knee stiffness with thigh amyotrophy.

CLINICAL DISCUSSION

The occurrence of MPNST on a giant solitary neurofibroma of the thigh is extremely rare. MRI allows evoking the diagnosis but radiologists are confronted with a problem of differential diagnosis. Histological examination supports the diagnosis in addition to immunohistochemical examination. Only surgical treatment can give hope for a cure. Recurrences remain frequent with a 5-year survival of 50 %.

CONCLUSION

Early diagnosis is essential to prevent the evolution of the tumor and the occurrence of poor prognostic factors compromising the management, increasing the risk of recurrence and affecting the overall survival of patients.

Clinical Characteristics and Management of Children and Adults with Neurofibromatosis Type 1 and Plexiform Neurofibromas in Denmark: A Nationwide Study

INTRODUCTION

Plexiform neurofibromas (PN) are benign nerve sheath tumours that are a frequent and potentially debilitating complication in patients with neurofibromatosis type 1 (NF1). The objective of this study was to describe the natural history of PN in children, adolescents and adults with NF1.

METHODS

This was a nationwide, longitudinal cohort study of patients with NF1 under observation at the two national centres of NF1 expertise in Denmark between 2000 and 2020. Patient and clinical characteristics were documented from individual medical records.

RESULTS

A total of 1099 patients with NF1 were included. Overall, 12% (35/296) of paediatric patients and 21% (172/803) of adult patients had ≥ 1 large PN (≥ 3 cm). Approximately half of patients with a large PN had ≥ 1 symptomatic PN. The most frequent symptoms were pain, neurological deficits, cosmetic issues, disfigurement, compression, increased psychosocial burden and vision loss. Clinical evaluations of PN size were available for 40 PN in 34 paediatric patients and 191 PN in 159 adult patients with large PN. Surgery (complete resection or debulking) was performed in 38% (15/40) of PN in paediatric patients and 45% (86/191) in adult patients. In addition, 35% of PN in paediatric patients and 33% in adult patients were inoperable. In a subgroup analysis, the overall PN size increased 1.06-fold per year. Malignant peripheral nerve sheath tumours (MPNST) were diagnosed in 21 patients (two paediatric and 19 adult patients).

CONCLUSIONS

This study shows that PN are common, their size and prevalence increase with age, many are often inoperable and pain and other symptoms are frequently associated. The results highlight the severe sequelae and unmet need for alternatives to analgesia and surgery in patients with PN.

A worldwide bibliometric analysis of malignant peripheral nerve sheath tumors from 2000 to 2022

Background

Currently, malignant peripheral nerve sheath tumors (MPNST) are the subject of intense research interest. However, bibliometric studies have not been conducted in this field. The purpose of the study was to identify historical trends and presents a bibliometric analysis of the MPNST literature from 2000 to 2022.

Methods

For the bibliometric analysis, publications were retrieved from the Web of Science database based on the following search terms: [TI = (MPNST) OR TI= (malignant peripheral nerve sheath tumors) AND PY = (2000-2022)]. The following information was collected for each document: the publication trends and geographical distribution, important authors and collaboration, keyword distribution and evaluation, most popular journals, and most influential articles.

Results

We included 1400 documents for bibliometric analysis, covering five categories: 824 articles, 17 proceedings papers, 68 letters, 402 meeting abstracts, and 89 reviews. Corrections, editorials, book chapters, data papers, publications with expressed concerns, and retractions were excluded from our research.

Conclusion

Since 2000, the number of publications on MPNST has continuously increased. Among all countries that contributed to the MPNST research, the USA, Japan, and China were the three most productive countries. The journal Modern Pathology has the most publications on MPNST, while those in the Cancer Research journal were the most frequently cited. The University of Texas MD Anderson Cancer Center may be a good partner to collaborate with. Recent research trends in MPNST have focused on tumorigenesis, clinical management, and predictive biomarkers.

Assessing the role of sodium fluorescein in peripheral nerve sheath tumors and mimicking lesions surgery: An update after 142 cases

Objective

Peripheral nerve sheath tumors (PNST) include mainly schwannomas and neurofibromas. Surgical resection represents the mainstay of treatment but due to their pathogenesis, distinguishing between intact functional nerve and the fibers from whence the PNST arose may not always be easy to perform, constituting the most relevant risk factor in determining a worsening in neurological condition. The introduction of intraoperative tools to better visualize these tumors could help achieve a gross-total resection. In this study, we analyzed the effect of sodium fluorescein (SF) on the visualization and resection of a large cohort of PNST.

Methods

Between September 2018 and December 2021, 142 consecutive patients harboring a suspected PNST underwent fluorescein-guided surgery at the Department of Neurosurgery of the Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy. All patients presented with a different degree of contrast enhancement at preoperative MRI. SF was intravenously injected after intubation at 1 mg/kg. Intraoperative fluorescein characteristics and postoperative neurological and radiological outcomes were collected, analyzed, and retrospectively compared with a historical series.

Results

142 patients were included (42 syndromic and 100 sporadic); schwannoma was the predominant histology, followed by neurofibroma (17 neurofibroma e 12 plexiform neurofibroma) and MPNST. Bright fluorescence was present in all cases of schwannomas and neurofibromas, although with a less homogeneous pattern, whereas it was significantly less evident for malignant PNST; perineurioma and hybrid nerve sheath tumors were characterized by a faint fluorescence enhancement. The surgical resection rate in the general population and even among the subgroups was about 66.7%; from the comparative analysis, we found a consistently higher rate of complete tumor removal in plexiform neurofibromas, 66% in the "fluorescent" group vs 44% in the "historical" group (p-value < 0.05). The rate of complications and mean surgical time were superimposable among the two populations.

Conclusions

SF is a valuable method for safe fluorescence-guided PNST and mimicking lesions resection. Our data showed a positive effect of fluorescein-guided surgery in increasing the rate of surgical resection of plexiform neurofibromas, suggesting a possible role in improving the functional and oncological outcome of these lesions.

Role of nerves in neurofibromatosis type 1-related nervous system tumors

BACKGROUND

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder that affects nearly 1 in 3000 infants. Neurofibromin inactivation and NF1 gene mutations are involved in various aspects of neuronal function regulation, including neuronal development induction, electrophysiological activity elevation, growth factor expression, and neurotransmitter release. NF1 patients often exhibit a predisposition to tumor development, especially in the nervous system, resulting in the frequent occurrence of peripheral nerve sheath tumors and gliomas. Recent evidence suggests that nerves play a role in the development of multiple tumor types, prompting researchers to investigate the nerve as a vital component in and regulator of the initiation and progression of NF1-related nervous system tumors.

CONCLUSION

In this review, we summarize existing evidence about the specific effects of NF1 mutation on neurons and emerging research on the role of nerves in neurological tumor development, promising a new set of selective and targeted therapies for NF1-related tumors.

Epidemiological profile and clinical characteristics of 491 Brazilian patients with neurofibromatosis type 1

BACKGROUND

Neurofibromatosis type 1 (NF1) is a chronic and progressive autosomal dominant genetic and sporadic disease characterized by cutaneous and neurological abnormalities. Plexiform neurofibroma (PN), a significant cause of clinical complications in NF-1, is a benign tumor of the peripheral nerve sheath that involves multiple nerve fascicles. Although there is an important number of patients who are affected by NF1 in Brazil, there is little data on the behavior of the disease in the national literature as well as in other low- and middle-income countries.

METHODS

We performed a retrospective analysis of 491 patients with NF1 followed at two reference centers in Brazil.

RESULTS

Approximately 38% of patients had PNs, resulting in reduced life quality. The median patient age with PNs was 30 years (range: 6 to 83 years). Head and neck, and extremity were the main affected locations with 35.8 and 30.6%, respectively. PNs were classified as asymptomatic in 25.1% of patients, while 52.5% presented symptomatic and inoperable tumors. The most common manifestations related to PNs were disfigurement and orthopedic involvement. Twenty patients developed neoplasms and ten (50%) presented with malignant peripheral nerve sheath tumors (MPNST). The prevalence of MPNST in our study was 2.9%.

CONCLUSIONS

Patients with NF1 experience clinically significant morbidity, especially when it is associated with PN. Though there are many patients affected by NF1 in Brazil and other low- and middle-income countries, there is little data available in the corresponding literature. Our results are comparable to the previous results reported from higher-income countries and international registries.

[Progress in diagnosis and treatment of neurofibromatosis in children]

Neurofibromatosis type 1（NF1） is an autosomal dominant genetic disease in which a mutation in the NF1 gene on chromosome 17q11.2 results in inactivation or down-regulation of neurofibromin. This results in a series of neurocutaneous lesions characterized by neurofibromatosis. Patients with plexiform neurofibromas（PN）, as one of the main manifestations of NF1, often experience pain, dysfunction, skeletal deformities, changes in appearance and other symptoms. In severe cases, compression of the airways and vital organs occurs, and the PN is at risk of malignancy progression. At present, its treatment is still challenging. Surgery is the primary treatment for PN, but complete resection is often difficult. In recent years, chemotherapy for PN has become a hot topic. This article reviews the research progress in the pathogenesis, diagnosis and treatment of PN in recent years.

Evaluation of magnetic resonance imaging-based radiomics characteristics for differentiation of benign and malignant peripheral nerve sheath tumors in neurofibromatosis type 1

BACKGROUND

Patients with neurofibromatosis type 1 (NF1) develop benign (BPNST), premalignant atypical (ANF), and malignant (MPNST) peripheral nerve sheath tumors. Radiological differentiation of these entities is challenging. Therefore, we aimed to evaluate the value of a magnetic resonance imaging (MRI)-based radiomics machine-learning (ML) classifier for differentiation of these three entities of internal peripheral nerve sheath tumors in NF1 patients.

METHODS

MRI was performed at 3T in 36 NF1 patients (20 male; age: 31 ± 11 years). Segmentation of 117 BPNSTs, 17 MPNSTs, and 8 ANFs was manually performed using T2w spectral attenuated inversion recovery sequences. One hundred seven features per lesion were extracted using PyRadiomics and applied for BPNST versus MPNST differentiation. A 5-feature radiomics signature was defined based on the most important features and tested for signature-based BPNST versus MPNST classification (random forest [RF] classification, leave-one-patient-out evaluation). In a second step, signature feature expressions for BPNSTs, ANFs, and MPNSTs were evaluated for radiomics-based classification for these three entities.

RESULTS

The mean area under the receiver operator characteristic curve (AUC) for the radiomics-based BPNST versus MPNST differentiation was 0.94, corresponding to correct classification of on average 16/17 MPNSTs and 114/117 BPNSTs (sensitivity: 94%, specificity: 97%). Exploratory analysis with the eight ANFs revealed intermediate radiomic feature characteristics in-between BPNST and MPNST tumor feature expression.

CONCLUSION

In this proof-of-principle study, ML using MRI-based radiomics characteristics allows sensitive and specific differentiation of BPNSTs and MPNSTs in NF1 patients. Feature expression of premalignant atypical tumors was distributed in-between benign and malignant tumor feature expressions, which illustrates biological plausibility of the considered radiomics characteristics.

Current concepts of neurofibromatosis type 1: pathophysiology and treatment

Neurofibromatosis type 1 is the most common tumor predisposition syndrome inherited in an autosomal dominant (100% penetrance) fashion with a wide variety of expressivity. From the perspective of plastic surgery, the most significant clinical symptoms, including disfiguration, peripheral neurologic symptoms, and skeletal abnormalities, are caused by various tumors originating from the affected nerves. Surgical removal is the standard of care for these tumors. However, the outcome is frequently unsatisfactory, facilitating the search for additional therapeutic adjuvants. Current trials of molecularly targeted therapies are promising.

The Lipid Asset Is Unbalanced in Peripheral Nerve Sheath Tumors

Peripheral nerve sheath tumors (PNSTs) include schwannomas, neurofibromas (NFs), and plexiform neurofibromas (PNFs), among others. While they are benign tumors, according to their biological behavior, some have the potential for malignant degeneration, mainly PNFs. The specific factors contributing to the more aggressive behavior of some PNSTs compared to others are not precisely known. Considering that lipid homeostasis plays a crucial role in fibrotic/inflammatory processes and in several cancers, we hypothesized that the lipid asset was also unbalanced in this group of nerve tumors. Through untargeted lipidomics, NFs presented a significant increase in ceramide, phosphatidylcholine, and Vitamin A ester. PNFs displayed a marked decrease in 34 out of 50 lipid class analyzed. An increased level of ether- and oxidized-triacylglycerols was observed; phosphatidylcholines were reduced. After sphingolipidomic analysis, we observed six sphingolipid classes. Ceramide and dihydroceramides were statistically increased in NFs. All the glycosylated species appeared reduced in NFs, but increased in PNFs. Our findings suggested that different subtypes of PNSTs presented a specific modulation in the lipidic profile. The untargeted and targeted lipidomic approaches, which were not applied until now, contribute to better clarifying bioactive lipid roles in PNS natural history to highlight disease molecular features and pathogenesis.

Clinical Outcomes and Prognostic Factors for Patients with Malignant Peripheral Nerve Sheath Tumour

Introduction

Few studies have described the characteristics and prognostic factors of patients with malignant peripheral nerve sheath tumour (MPNST). In this study, we retrospectively investigated the clinicopathological features, clinical outcomes, and prognostic factors of these patients. Patients and Methods. We recruited patients with MPNST who were treated at our institutions from 1991 to 2020. We collected and statistically analysed information on patient-, tumour-, and treatment-related factors. The median follow-up period was 61 months (range, 1-335.8 months).

Results

A total of 60 patients (31 males, 29 females) with a median age of 55 years (range, 8-84 years) at initial diagnosis were included. The median tumour size was 7 cm (range, 1.6-30 cm) in the greatest dimension. The 5-year overall survival (OS) rate of all patients was 69.5%. Univariate analysis revealed that large-sized tumour, metastasis at diagnosis, and no surgery of the primary tumour were significantly associated with patients with worse OS. Multivariate analysis identified surgery of the primary tumour as an independent prognostic factor for improved OS. Among patients with localised disease at diagnosis who underwent surgery of the primary tumour at our institutions, the 5-year OS, local recurrence-free survival (LRFS), and metastasis-free survival (MFS) rates were 81.1%, 78.2%, and 70.3%, respectively. Univariate analysis revealed that positive surgical margin was significantly correlated with unfavourable OS and LRFS, and high grade was a poor prognostic indicator for MFS.

Conclusion

Complete surgical resection with negative surgical margins is necessary for a successful MPNST treatment. Multidisciplinary management of MPNST with aggressive features is important for optimising patient outcomes.

Malignant Peripheral Nerve Sheath Tumor Arising from Small Bowel Mesentery: an Extremely Rare Case with Review of Literature

PURPOSE

Malignant peripheral nerve sheath tumor (MPNST) of small bowel mesentery is a rare tumor. We report a rare case of MPNST of small bowel mesentery in a patient without neurofibromatosis (NF).

METHODS

A 50-year-old male, with no features suggestive of NF1, presented to us with complaints of pain abdomen. Contrast-enhanced computed tomography (CECT) of the abdomen revealed a mass in the infrarenal region. On laparotomy, mass was seen to be arising from the mesentery of the jejunum. En-bloc resection of the tumor was done, and histopathological examination was suggestive of malignant peripheral nerve sheath tumor of the small bowel mesentery.

RESULT

Patient received adjuvant external beam radiotherapy to a dose of 50.4 Gy to the tumor bed. The patient was planned for chemotherapy but absconded and later came with recurrence. The patient finally succumbed to disease.

CONCLUSION

Surgery is the mainstay of treatment. Adjuvant treatment should be based on histopathological report.

Congenital Pigmentary Anomalies in the Newborn

Congenital pigmentary anomalies may be evident at birth or soon after, with some birthmarks becoming apparent later in infancy or early childhood. It is important to recognize various pigmentary anomalies in the neonate, most of which are benign but a subset of which are associated with cutaneous morbidity or systemic ramifications and require further evaluation. This review will focus on pigmentary mosaicism, congenital melanocytic nevi, nevus spilus, dermal melanocytosis, and pigmentary anomalies associated with neurofibromatosis type 1 (café au lait spots, freckling, plexiform neurofibromas, nevus anemicus), tuberous sclerosis (hypomelanotic macules), and incontinentia pigmenti.

Parotid Neurogenic Tumors: MPNST Sarcoma to Schwannoma-Review of Literature and Guidelines in Management

Objective

To delineate a distinct clinical, pathological, cytoimmunohistochemical distinguishing features of extracranial parotid neurogenic tumors. Pleomorphic adenoma, the most common parotid neoplasm by itself can mimic a neurogenic tumor, i.e., schwannoma. We have reported such rare entity in earlier publications. This is a systematic review with a case discussion of the third only documented malignant peripheral nerve sheath tumor (MPNST) arising in the parotid in a noncontiguous fashion. We review the management, diagnostic immunohistochemistry of this low-grade sarcoma, which has not been documented thus far.

Purpose

Significant diagnostic and management pitfalls may occur even with fine-needle aspiration or biopsy, as they will not be ideal in diagnosis of parotid neurogenic neoplasms preoperatively. Ultrasound as well as magnetic resonance imaging may not offer a specific facial nerve course in association to the neoplastic lesion. Majority of the neurogenic tumors can be misdiagnosed and hence, improperly managed leading to facial nerve injury and tumor morbidity. Due to the lack of ideal diagnostic modality and morbidity of facial nerve injury, a thorough review of differential diagnosis inclusive of neurogenic tumors of the parotid is to be considered in indications of surgical approaches. We retrospectively review successful resection with preservation of facial nerve function in our parotid neurogenic tumors.

Conclusion

The objective of this paper is to review the guidelines and treatment planning of parotid neurogenic tumors.

Severe Phenotype in Patients with Large Deletions of NF1

Complete deletion of the NF1 gene is identified in 5-10% of patients with neurofibromatosis type 1 (NF1). Several studies have previously described particularly severe forms of the disease in NF1 patients with deletion of the NF1 locus, but comprehensive descriptions of large cohorts are still missing to fully characterize this contiguous gene syndrome. NF1-deleted patients were enrolled and phenotypically characterized with a standardized questionnaire between 2005 and 2020 from a large French NF1 cohort. Statistical analyses for main NF1-associated symptoms were performed versus an NF1 reference population. A deletion of the NF1 gene was detected in 4% (139/3479) of molecularly confirmed NF1 index cases. The median age of the group at clinical investigations was 21 years old. A comprehensive clinical assessment showed that 93% (116/126) of NF1-deleted patients fulfilled the NIH criteria for NF1. More than half had café-au-lait spots, skinfold freckling, Lisch nodules, neurofibromas, neurological abnormalities, and cognitive impairment or learning disabilities. Comparison with previously described "classic" NF1 cohorts showed a significantly higher proportion of symptomatic spinal neurofibromas, dysmorphism, learning disabilities, malignancies, and skeletal and cardiovascular abnormalities in the NF1-deleted group. We described the largest NF1-deleted cohort to date and clarified the more severe phenotype observed in these patients.

Genotype-Phenotype Associations in Patients With Type-1, Type-2, and Atypical NF1 Microdeletions

Neurofibromatosis type 1 is a tumor predisposition syndrome inherited in autosomal dominant manner. Besides the intragenic loss-of-function mutations in NF1 gene, large deletions encompassing the NF1 gene and its flanking regions are responsible for the development of the variable clinical phenotype. These large deletions titled as NF1 microdeletions lead to a more severe clinical phenotype than those observed in patients with intragenic NF1 mutations. Around 5-10% of the cases harbor large deletion and four major types of NF1 microdeletions (type 1, 2, 3 and atypical) have been identified so far. They are distinguishable in term of their size and the location of the breakpoints, by the frequency of somatic mosaicism with normal cells not harboring the deletion and by the number of the affected genes within the deleted region. In our study genotype-phenotype analyses have been performed in 17 mostly pediatric patients with NF1 microdeletion syndrome identified by multiplex ligation-dependent probe amplification after systematic sequencing of the NF1 gene. Confirmation and classification of the NF1 large deletions were performed using array comparative genomic hybridization, where it was feasible. In our patient cohort 70% of the patients possess type-1 deletion, one patient harbors type-2 deletion and 23% of our cases have atypical NF1 deletion. All the atypical deletions identified in this study proved to be novel. One patient with atypical deletion displayed mosaicism. In our study NF1 microdeletion patients presented dysmorphic facial features, macrocephaly, large hands and feet, delayed cognitive development and/or learning difficulties, speech difficulties, overgrowth more often than patients with intragenic NF1 mutations. Moreover, neurobehavior problems, macrocephaly and overgrowth were less frequent in atypical cases compared to type-1 deletion. Proper diagnosis is challenging in certain patients since several clinical manifestations show age-dependency. Large tumor load exhibited more frequently in this type of disorder, therefore better understanding of genotype-phenotype correlations and progress of the disease is essential for individuals suffering from neurofibromatosis to improve the quality of their life. Our study presented additional clinical data related to NF1 microdeletion patients especially for pediatric cases and it contributes to the better understanding of this type of disorder.

Genotype-phenotype correlation in neurofibromatosis type-1: NF1 whole gene deletions lead to high tumor-burden and increased tumor-growth

Neurofibromatosis type-1 (NF1) patients suffer from cutaneous and subcutaneous neurofibromas (CNF) and large plexiform neurofibromas (PNF). Whole gene deletions of the NF1 gene can cause a more severe phenotype compared to smaller intragenic changes. Two distinct groups of NF1 whole gene deletions are type-1 deletions and atypical deletions. Our aim was to assess volumes and averaged annual growth-rates of CNF and PNF in patients with NF1 whole gene deletions and to compare these with NF1 patients without large deletions of the NF1 gene. We retrospectively evaluated 140 whole-body MR examinations of 38 patients with NF1 whole gene deletions (type-1 group: n = 27/atypical group n = 11) and an age- and sex matched collective of 38 NF1-patients. Age-dependent subgroups were created (0-18 vs >18 years). Sixty-four patients received follow-up MRI examinations (NF1whole gene deletion n = 32/control group n = 32). Whole-body tumor-volumes were semi-automatically assessed (MedX, V3.42). Tumor volumes and averaged annual growth-rates were compared. Median tumor-burden was significantly higher in the type-1 group (418ml; IQR 77 - 950ml, p = 0.012) but not in the atypical group (356ml;IQR 140-1190ml, p = 0.099) when compared to the controls (49ml; IQR 11-691ml). Averaged annual growth rates were significantly higher in both the type-1 group (14%/year; IQR 45-36%/year, p = 0.004) and atypical group (11%/year; IQR 5-23%/year, p = 0.014) compared to the controls (4%/year; IQR1-8%/year). Averaged annual growth rates were significantly higher in pediatric patients with type-1 deletions (21%/year) compared with adult patients (8%/year, p = 0.014) and also compared with pediatric patients without large deletions of the NF1 gene (3.3%/year, p = 0.0015). NF1 whole gene deletions cause a more severe phenotype of NF1 with higher tumor burden and higher growth-rates compared to NF1 patients without large deletions of the NF1 gene. In particular, pediatric patients with type-1 deletions display a pronounced tumor growth.

Malignant transformation in a sciatic plexiform neurofibroma in Neurofibromatosis Type 1 - imaging features that aid diagnosis

A 41-year-old Asian male with NF1 and bilateral sciatic plexiform neurofibromas, presented with unintentional weight loss, increasing size of a left thigh mass associated with increasing pain and radiculopathy. MRI of the left thigh demonstrated imaging features suspicious of malignant transformation. The patient had a new left lung mass, demonstrating avid FDG uptake, raising suspicion for metastasis. Surgical resection of the left thigh mass confirms malignant transformation in a preexisting sciatic plexiform neurofibroma. Diagnosis of malignant transformation in a nerve sheath tumour can be challenging. MRI remains the main preferred imaging modality in the evaluation of these tumours. Imaging features that raise suspicion for malignant transformation are discussed. Although none of these are specific for malignant transformation, studies suggest that the presence of two to four of these features should prompt further investigations.

Longitudinal evaluation of peripheral nerve sheath tumors in neurofibromatosis type 1: growth analysis of plexiform neurofibromas and distinct nodular lesions

BACKGROUND

Understanding the natural history of non-malignant peripheral nerve sheath tumors (PNSTs) in neurofibromatosis type 1 (NF1) is critical to optimal clinical care and the development of meaningful clinical trials.

METHODS

We longitudinally analyzed growth of plexiform neurofibromas (PNs) and of PNSTs with distinct nodular appearance (distinct nodular lesions [DNLs]) using volumetric MRI analysis in patients enrolled on a natural history study (NCT00924196).

RESULTS

DNLs were observed in 58/122 (45.6%) patients (median 2 DNLs/patient). In DNLs that developed during follow-up, median age of development was 17 years. A moderate negative correlation was observed between the estimated PN growth rate and patients' age at initial MRI (Spearman's r [95% CI]: -0.60 [-0.73, -0.43], n = 70), whereas only a weak correlation was observed for DNLs (Spearman's r [95% CI]: -0.25 [-0.47, 0.004]; n = 61). We observed a moderate negative correlation between tumor growth rate and baseline tumor volume for PNs and DNLs (Spearman's r [95% CI]: -0.52 [-0.67, -0.32] and -0.61 [-0.75, -0.42], respectively). Spontaneous tumor volume reduction was observed in 10 PNs and 7 DNLs (median decrease per year, 3.6% and 7.3%, respectively).

CONCLUSION

We corroborate previously described findings that most rapidly growing PNs are observed in young children. DNLs tend to develop later in life and their growth is minimally age related. Distinct growth characteristics of PNs and DNLs suggest that these lesions have a different biology and may require different clinical management and clinical trial design. In a subset of PNs and DNLs, slow spontaneous regression in tumor volume was seen.

Whole-Body MRI Surveillance of Cancer Predisposition Syndromes: Current Best Practice Guidelines for Use, Performance, and Interpretation

OBJECTIVE. Whole-body MRI is a valuable tool in the surveillance of cancer predisposition syndromes (CPSs). Because it allows wide-FOV imaging without ionizing radiation, whole-body MRI is ideal in pediatric patients, enabling efficient assessment of different organ systems for multifocal disease. This article summarizes the use of whole-body MRI in pediatric patients with CPSs for earlier detection of malignancy, provides evidence where available, and offers guidance where lacking because of the rarity of CPSs. Protocol modifications and technique performance in specific CPSs are also considered. CONCLUSION. Whole-body MRI is the preferred imaging modality for surveillance of pediatric patients with CPSs, and the growing literature supports its importance in presymptomatic cancer detection.

Diagnosis and management of malignant peripheral nerve sheath tumors: Current practice and future perspectives

One of the most common malignancies affecting adults with the neurofibromatosis type 1 (NF1) cancer predisposition syndrome is the malignant peripheral nerve sheath tumor (MPNST), a highly aggressive sarcoma that typically develops from benign plexiform neurofibromas. Approximately 8-13% of individuals with NF1 will develop MPNST during young adulthood. There are few therapeutic options, and the vast majority of people with these cancers will die within 5 years of diagnosis. Despite efforts to understand the pathogenesis of these aggressive tumors, the overall prognosis remains dismal. This manuscript will review the current understanding of the cellular and molecular progression of MPNST, diagnostic workup of patients with these tumors, current treatment paradigms, and investigational treatment options. Additionally, we highlight novel areas of preclinical research, which may lead to future clinical trials. In summary, MPNST remains a diagnostic and therapeutic challenge, and future work is needed to develop novel and rational combinational therapy for these tumors.

Neurological malignancies in neurofibromatosis type 1

PURPOSE OF REVIEW

The current review summarizes recent advances on three important issues in neurofibromatosis type 1 (NF1) management: the identification of specific NF1 gene mutations predicting the risk for developing neurological malignancies; the molecular features of NF1-associated tumors and their differences from sporadic neoplasms; genetic, epigenetic, or microenviromental factors leading benign tumors to a malignant transformation in NF1.

RECENT FINDINGS

The association between the risk of developing optic pathway glioma and specific germiline NF1 mutations is still debated and further studies are needed with large, new cohorts of patients. The available evidences suggest that gliomas and malignant peripheral nerve sheath tumors (MPNSTs) in NF1 have a distinct genetic signatures, different from those observed in sporadic neoplasms. Some neoplasms, very rare in general population, such as subependymal giant cell astrocytoma, can be observed in NF1. A subgroup of low-grade NF1-gliomas, some MPNSTs and plexiform neurofibromas contain abundant T lymphocyte infiltrates suggesting that immunotherapy could be a potential therapeutic approach.

SUMMARY

These data support the notion that next-generation sequencing efforts are helpful in the genetic characterization of NF1-associated malignancies A better knowledge of those tumors at the genomic level, is essential for addressing new treatments and may contribute to a deeper comprehension of NF1/RAS signaling also in sporadic cancers.

Combined Targeting of AKT and mTOR Inhibits Proliferation of Human NF1-Associated Malignant Peripheral Nerve Sheath Tumour Cells In Vitro but not in a Xenograft Mouse Model In Vivo

Persistent signalling via the PI3K/AKT/mTOR pathway is a major driver of malignancy in NF1-associated malignant peripheral nerve sheath tumours (MPNST). Nevertheless, single targeting of this pathway is not sufficient to inhibit MPNST growth. In this report, we demonstrate that combined treatment with the allosteric pan-AKT inhibitor MK-2206 and the mTORC1/mTORC2 inhibitor AZD8055 has synergistic effects on the viability of MPNST cell lines in comparison to the treatment with each compound alone. However, when treating animals bearing experimental MPNST with the combined AKT/mTOR regime, no influence on tumour growth was observed. Further analysis of the MPNST xenograft tumours resistant to AKT/mTOR treatment revealed a reactivation of both AKT and mTOR in several tumour samples. Additional targeting of the RAS/RAF/MEK/MAPK pathway with the allosteric MEK1/2 inhibitor AZD6244 showed synergistic effects on the viability of MPNST cell lines in vitro in comparison to the dual AKT/mTOR inhibition. In summary, these data indicate that combined treatment with AKT and mTOR inhibitors is effective on MPNST cells in vitro but tumour resistance can occur rapidly in vivo by restoration of AKT/mTOR signalling. Our data further suggest that a triple treatment with inhibitors against AKT, mTORC1/2 and MEK1/2 may be a promising treatment option that should be further analysed in an experimental MPNST mouse model in vivo.

Deregulated microRNAs in neurofibromatosis type 1 derived malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNST) are aggressive cancers that occur spontaneously (sporadic MPNST) or from benign plexiform neurofibromas in neurofibromatosis type 1 (NF1) patients. MPNSTs metastasize easily, are therapy resistant and are frequently fatal. The molecular changes underlying the malignant transformation in the NF1 setting are incompletely understood. Here we investigate the involvement of microRNAs in this process. MicroRNA expression profiles were determined from a series of archival, paired samples of plexiform neurofibroma and MPNST. Ninety differentially expressed microRNAs were identified between the paired samples. Three downregulated microRNAs (let-7b-5p, miR-143-3p, miR-145-5p) and two upregulated microRNAs (miR135b-5p and miR-889-3p) in MPNST were selected for functional characterization. In general, their differential expression was validated in a relevant cell line panel but only partly in a series of unpaired, fresh frozen tumor samples. As part of the validation process we also analyzed microRNA expression profiles of sporadic MPNSTs observing that microRNA expression discriminates NF1-associated and sporadic MPNSTs. The role of microRNAs in cancer progression was examined in NF1-derived MPNST cell lines by transiently modulating microRNA levels. Our findings indicate that some microRNAs affect migratory and invasive capabilities and Wnt signaling activity but the effects are distinct in different cell lines. We conclude that miRNAs play essential regulatory roles in MPNST facilitating tumor progression.

Phakomatoses

Phakomatoses present with characteristic findings on the skin, central or peripheral nervous system, and tumors. Neurofibromatosis type 1 is the most common syndrome and is characterized by Café-au-lait macules, intertriginous freckling, Lisch nodules, and tumors including neurofibromas, malignant peripheral nerve sheath tumors, and gliomas. Tuberous Sclerosis Complex is characterized by benign hamartomas presenting with hypomelanotic macules, shagreen patches, angiofibromas, confetti lesions and tumors including cortical tubers, subependymal nodules, subependymal giant cell astrocytomas and tumors of the kidney, lung, and heart. Managing these disorders requires disease specific supportive care, tumor monitoring, surveillance for selected cancers, and treatment of comorbid conditions.

Neurofibromatosis 1 French national guidelines based on an extensive literature review since 1966

Neurofibromatosis type 1 is a relatively common genetic disease, with a prevalence ranging between 1/3000 and 1/6000 people worldwide. The disease affects multiple systems with cutaneous, neurologic, and orthopedic as major manifestations which lead to significant morbidity or mortality. Indeed, NF1 patients are at an increased risk of malignancy and have a life expectancy about 10-15 years shorter than the general population. The mainstay of management of NF1 is a patient-centered longitudinal care with age-specific monitoring of clinical manifestations, aiming at the early recognition and symptomatic treatment of complications as they occur. Protocole national de diagnostic et de soins (PNDS) are mandatory French clinical practice guidelines for rare diseases required by the French national plan for rare diseases. Their purpose is to provide health care professionals with guidance regarding the optimal diagnostic and therapeutic management of patients affected with a rare disease; and thus, harmonizing their management nationwide. PNDS are usually developed through a critical literature review and a multidisciplinary expert consensus. The purpose of this article is to present the French guidelines on NF1, making them even more available to the international medical community. We further dwelled on the emerging new evidence that might have therapeutic potential or a strong impact on NF1 management in the coming feature. Given the complexity of the disease, the management of children and adults with NF1 entails the full complement healthcare providers and communication among the various specialties.

Giant Malignant Peripheral Nerve Sheath Tumor of the Head and Neck: A Case Report and Literature Review

Malignant peripheral nerve sheath tumor (MPNST) is a malignant soft tissue sarcoma with high mortality, low morbidity, and poor prognosis. The MPNST occurs mostly in the limbs and torso, and rarely in the head and neck. However, MPNST is insensitive to radiotherapy and chemotherapy, and complete surgical resection with negative margin is the most important and effective strategy. We present a case of MPNST in the head and neck. The tumor invades the left temporal bone, petrous bone, and mastoid bone, and compression changes in the focal cerebellum and sigmoid sinus. The patient underwent the left temporal region tumor resection + surgical reconstruction with temporalis muscle flap and pectoralis major myocutaneous flap. Adjuvant radiotherapy (55 Gy) was given after surgery, and there were no local recurrence and distant metastasis after 31-month follow-up.

Clinical characterization of children and adolescents with NF1 microdeletions

PURPOSE

An estimated 5-11% of patients with neurofibromatosis type 1 (NF1) harbour NF1 microdeletions encompassing the NF1 gene and its flanking regions. The purpose of this study was to evaluate the clinical phenotype in children and adolescents with NF1 microdeletions.

METHODS

We retrospectively analysed 30 children and adolescents with NF1 microdeletions pertaining to externally visible neurofibromas. The internal tumour load was determined by volumetry of whole-body magnetic resonance imaging (MRI) in 20 children and adolescents with NF1 microdeletions. Furthermore, the prevalence of global developmental delay, autism spectrum disorder and attention deficit hyperactivity disorder (ADHD) were evaluated.

RESULTS

Children and adolescents with NF1 microdeletions had significantly more often cutaneous, subcutaneous and externally visible plexiform neurofibromas than age-matched patients with intragenic NF1 mutations. Internal neurofibromas were detected in all 20 children and adolescents with NF1 microdeletions analysed by whole-body MRI. By contrast, only 17 (61%) of 28 age-matched NF1 patients without microdeletions had internal tumours. The total internal tumour load was significantly higher in NF1 microdeletion patients than in NF1 patients without microdeletions. Global developmental delay was observed in 28 (93%) of 30 children with NF1 microdeletions investigated. The mean full-scale intelligence quotient in our patient group was 77.7 which is significantly lower than that of patients with intragenic NF1 mutations. ADHD was diagnosed in 15 (88%) of 17 children and adolescents with NF1 microdeletion. Furthermore, 17 (71%) of the 24 patients investigated had T-scores ≥ 60 up to 75, indicative of mild to moderate autistic symptoms, which are consequently significantly more frequent in patients with NF1 microdeletions than in the general NF1 population. Also, the mean total T-score was significantly higher in patients with NF1 microdeletions than in the general NF1 population.

CONCLUSION

Our findings indicate that already at a very young age, NF1 microdeletions patients frequently exhibit a severe disease manifestation which requires specialized long-term clinical care.

The Diagnosis and Management of Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1), NF2, and schwannomatosis are related, but distinct, tumor suppressor syndromes characterized by a predilection for tumors in the central and peripheral nervous systems. NF1 is one of the most common autosomal dominant conditions of the nervous system. NF1 has a high degree of variability in clinical presentation, which may include multiple neoplasms as well as cutaneous, vascular, bony, and cognitive features. Some of these manifestations overlap with other genetic conditions. Accurate diagnosis of NF1 is important for individualizing clinical care and genetic counseling. This article summarizes the clinical features, diagnostic work-up, and management of NF1.

One NF1 Mutation may Conceal Another

Neurofibromatosis type 1 (NF1) is an autosomal dominant disease with complete penetrance but high variable expressivity. NF1 is caused by loss-of-function mutations in the NF1 gene, a negative regulator of the RAS-MAPK pathway. The NF1 gene has one of the highest mutation rates in human disorders, which may explain the outbreak of independent de novo variants in the same family. Here, we report the co-occurrence of pathogenic variants in the NF1 and SPRED1 genes in six families with NF1 and Legius syndrome, using next-generation sequencing. In five of these families, we observed the co-occurrence of two independent NF1 variants. All NF1 variants were classified as pathogenic, according to the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG-AMP) guidelines. In the sixth family, one sibling inherited a complete deletion of the NF1 gene from her mother and carried a variant of unknown significance in the SPRED1 gene. This variant was also present in her brother, who was diagnosed with Legius syndrome, a differential diagnosis of NF1. This work illustrates the complexity of molecular diagnosis in a not-so-rare genetic disease.

Screening populations at high risk for soft tissue sarcoma and surveillance following soft tissue sarcoma resection

Soft tissue sarcomas (STS) are a rare and diverse group of tumors that affect both adult and pediatric populations. This review discusses current screening recommendations for populations at increased risk for STS, including those with genetic predispositions. We also review surveillance guidelines for those at risk for recurrence following curative-intent surgery.

The PTEN Tumor Suppressor Gene in Soft Tissue Sarcoma

Soft tissue sarcoma (STS) is a rare malignancy of mesenchymal origin classified into more than 50 different subtypes with distinct clinical and pathologic features. Despite the poor prognosis in the majority of patients, only modest improvements in treatment strategies have been achieved, largely due to the rarity and heterogeneity of these tumors. Therefore, the discovery of new prognostic and predictive biomarkers, together with new therapeutic targets, is of enormous interest. Phosphatase and tensin homolog (PTEN) is a well-known tumor suppressor that commonly loses its function via mutation, deletion, transcriptional silencing, or protein instability, and is frequently downregulated in distinct sarcoma subtypes. The loss of PTEN function has consequent alterations in important pathways implicated in cell proliferation, survival, migration, and genomic stability. PTEN can also interact with other tumor suppressors and oncogenic signaling pathways that have important implications for the pathogenesis in certain STSs. The aim of the present review is to summarize the biological significance of PTEN in STS and its potential role in the development of new therapeutic strategies.

How Effective Are Noninvasive Tests for Diagnosing Malignant Peripheral Nerve Sheath Tumors in Patients with Neurofibromatosis Type 1? Diagnosing MPNST in NF1 Patients

Background

Distinguishing between benign and malignant peripheral nerve sheath tumors (MPNSTs) in neurofibromatosis 1 (NF1) patients prior to excision can be challenging. How can MPNST be most accurately diagnosed using clinical symptoms, magnetic resonance imaging (MRI) findings (tumor size, depth, and necrosis), positron emission tomography (PET) measures (SUV_peak, SUV_max, SUV_{max tumor}/SUV_{mean liver}, and qualitative scale), and combinations of the above? Methods. All NF1 patients who underwent PET imaging at our institution (January 1, 2007–December 31, 2016) were included. Medical records were reviewed for clinical findings; MR images and PET images were interpreted by two fellowship-trained musculoskeletal and nuclear medicine radiologists, respectively. Receiver operating characteristic (ROC) curves were created for each PET measurement; the area under the curve (AUC) and thresholds for diagnosing malignancy were calculated. Logistic regression determined significant predictors of malignancy.

Results

Our population of 41 patients contained 34 benign and 36 malignant tumors. Clinical findings did not reliably predict MPNST. Tumor depth below fascia was highly sensitive; larger tumors were more likely to be malignant but without a useful cutoff for diagnosis. Necrosis on MRI was highly accurate and was the only significant variable in the regression model. PET measures were highly accurate, with AUCs comparable and cutoff points consistent with prior studies. A diagnostic algorithm was created using MRI and PET findings.

Conclusions

MRI and PET were more effective at diagnosing MPNST than clinical features. We created an algorithm for preoperative evaluation of peripheral nerve sheath tumors in NF1 patients, for which additional validation will be indicated.

Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation

PURPOSE

Neurofibromatosis type 1 (NF1) is characterized by a highly variable clinical presentation, but almost all NF1-affected adults present with cutaneous and/or subcutaneous neurofibromas. Exceptions are individuals heterozygous for the NF1 in-frame deletion, c.2970_2972del (p.Met992del), associated with a mild phenotype without any externally visible tumors.

METHODS

A total of 135 individuals from 103 unrelated families, all carrying the constitutional NF1 p.Met992del pathogenic variant and clinically assessed using the same standardized phenotypic checklist form, were included in this study.

RESULTS

None of the individuals had externally visible plexiform or histopathologically confirmed cutaneous or subcutaneous neurofibromas. We did not identify any complications, such as symptomatic optic pathway gliomas (OPGs) or symptomatic spinal neurofibromas; however, 4.8% of individuals had nonoptic brain tumors, mostly low-grade and asymptomatic, and 38.8% had cognitive impairment/learning disabilities. In an individual with the NF1 constitutional c.2970_2972del and three astrocytomas, we provided proof that all were NF1-associated tumors given loss of heterozygosity at three intragenic NF1 microsatellite markers and c.2970_2972del.

CONCLUSION

We demonstrate that individuals with the NF1 p.Met992del pathogenic variant have a mild NF1 phenotype lacking clinically suspected plexiform, cutaneous, or subcutaneous neurofibromas. However, learning difficulties are clearly part of the phenotypic presentation in these individuals and will require specialized care.