Molecular, genetic, and cellular pathogenesis of neurofibromas and surgical implications

Recurrent Schwannomatosis of the Hand

Background: Peripheral nerve sheath tumors (PNSTs) are neoplastic soft tissue masses generated from the abnormal proliferation of Schwann cells. Often, these tumors occur in isolation and are known as schwannomas or neurilemmomas. The presence of multiple schwannomas is known as schwannomatosis. The purpose of this article is 2-fold: (1) to review the relevant literature and describe a unique case of this rare condition; and (2) to emphasize salient clinical considerations in the diagnosis and treatment of schwannomatosis. Methods: In this report, we describe the case of a 52-year-old white man who presented with multiple recurrent soft tissue masses of the right hand. On initial presentation, he described pain across his right hand and index finger, which persisted despite numerous prior operations. The index finger had a flexion contracture around the location of the proximal interphalangeal joint, and there were multiple tender masses along the length of the finger and palm. Results: Segmental excision of the affected radial digital nerve was performed. A pulp flap based on contralateral neurovascular bundle resulted in a sensate, pain-free digit. Tissue pathology confirmed the diagnosis of multiple neurilemmomas. Conclusions: We report the success of a radial digital neurectomy in a patient with widespread neurilemmomas, who had previously excluded that painful digit from use. It was through careful consideration of the preoperative differential diagnosis, by valuing the preoperative imaging, and by considering all surgical options with specific attention paid to skin flap design that this good outcome of a fully sensate, pain-free, mobile index finger was achieved.

Computational insights of K1444N substitution in GAP-related domain of NF1 gene associated with neurofibromatosis type 1 disease: a molecular modeling and dynamics approach

The NF1 gene encodes for neurofibromin protein, which is ubiquitously expressed, but most highly in the central nervous system. Non-synonymous SNPs (nsSNPs) in the NF1 gene were found to be associated with Neurofibromatosis Type 1 disease, which is characterized by the growth of tumors along nerves in the skin, brain, and other parts of the body. In this study, we used several in silico predictions tools to analyze 16 nsSNPs in the RAS-GAP domain of neurofibromin, the K1444N (K1423N) mutation was predicted as the most pathogenic. The comparative molecular dynamic simulation (MDS; 50 ns) between the wild type and the K1444N (K1423N) mutant suggested a significant change in the electrostatic potential. In addition, the RMSD, RMSF, Rg, hydrogen bonds, and PCA analysis confirmed the loss of flexibility and increase in compactness of the mutant protein. Further, SASA analysis revealed exchange between hydrophobic and hydrophilic residues from the core of the RAS-GAP domain to the surface of the mutant domain, consistent with the secondary structure analysis that showed significant alteration in the mutant protein conformation. Our data concludes that the K1444N (K1423N) mutant lead to increasing the rigidity and compactness of the protein. This study provides evidence of the benefits of the computational tools in predicting the pathogenicity of genetic mutations and suggests the application of MDS and different in silico prediction tools for variant assessment and classification in genetic clinics.

Neurofibromatosis type 1-associated multiple rectal neuroendocrine tumors: A case report and review of the literature

Neurofibromatosis type 1 (NF-1) is commonly associated with benign or malignant tumors in both the central and peripheral nervous systems. However, rare cases of NF-1-associated multiple rectal neuroendocrine tumors have been reported. This report describes a case of a 39 year old female with NF-1 and intermittent hematochezia as a primary symptom. Physical examination showed multiple subcutaneous nodules and café au lait spots with obvious scoliosis of the back. Imaging examinations and colonoscopy found malformation of the left external iliac vein and multiple gray-yellow nodules with varying sizes and shapes in the rectal submucosal layer. Histological and immunohistochemical results suggested multiple rectal neuroendocrine tumors, a rare disease with few appreciable symptoms and a particularly poor prognosis. The patient with NF-1 presented here had not only multiple rectal neuroendocrine neoplasms but also vascular malformations, scoliosis and other multiple system lesions. This case therefore contributes to improving clinical understanding, diagnosis and treatment of related complications for patients with NF-1 who present with associated medical conditions.

Neurofibroma of the Colon: A Diagnostic Mimicker of Gastrointestinal Stromal Tumor

Gastrointestinal neurofibroma usually develops as diffuse gastrointestinal involvement in neurofibromatosis type 1 patients. Only 4 cases of sporadic colonic neurofibroma in a patient without neurofibromatosis type 1 have been reported in the English literature. A 26-year-old female patient underwent colonoscopy, and a 4-cm-sized polypoid mass was identified in the sigmoid colon. Wedge resection of the mass showed a yellowish, hard submucosal tumor. Microscopically, the tumor was composed of wavy spindle cells, fibroblasts, and strands of collagen; the stroma showed scattered myxoid areas. The differential diagnoses included gastrointestinal stromal tumor, schwannoma, and neurofibroma. Immunohistochemistry for c-Kit, DOG (discovered on gastrointestinal stromal tumors)-1, smooth muscle actin, S-100 protein, and CD34 was performed. The tumor cells were diffusely positive for CD34 and S-100 protein, while they were completely negative for c-Kit, DOG-1, and smooth muscle actin. The final diagnosis was neurofibroma. Sporadic colonic neurofibroma is very rare. Given the diffuse positivity for CD34 and its rarity, colonic neurofibroma can be easily misdiagnosed as gastrointestinal stromal tumor. Recognition of this entity would be beneficial for pathologists to avoid misdiagnosis and unnecessary treatment.

Management of Giant Facial Neurofibroma With Intratumoral Hematoma in Neurofibromatosis Type 1 Patient

Type-1 neurofibromatosis, a common autosomal dominant disease, is also known as von Recklinghausen disease. Surgical procedures to treat this condition are challenging because of the brittleness of the surrounding blood vessels and soft tissues that bring the risk of causing fatal bleeding. With improvements in neurovascular embolization procedures, some literatures have been published about the application of preoperative embolization for neurofibromatosis. This case report describes a 60-year-old female with Type-1 neurofibromatosis, who presented giant facial neurofibromas with intratumoral hemorrhage on both cheeks. This patient demonstrates that these huge and challenging lesions can be successfully treated with preoperative embolization and surgical treatment. We also discuss the timing of surgical treatment with such lesions.

Sudden death due to rupture of the right internal carotid artery in neurofibromatosis type 1: A case report

Vascular involvement is a well-recognized manifestation of neurofibromatosis type 1 (NF1) which has the potential to be fatal when disrupted. We here present a case of sudden death due to the fatal arterial rupture resulted from infiltration of the neurofibromas. A 42-year-old man who suffered from NF1 presented a 1-h history of sudden onset of pain in his right cervical region. His condition worsened and became unconscious on his way to the emergency room. Despite resuscitation efforts, he died 30min later without regaining consciousness. Autopsy examination showed that a neurofibroma located around the right internal carotid artery, confirmed immunohistochemically with S-100, vimentin and CD34. Furthermore, proliferation of spindle cells positive for S-100 was seen in the wall of right internal carotid artery, which was disrupted and resulted in a hemorrhage. These findings suggest that the artery was disrupted by neurofibromas in the vascular wall, which led to fragility of the vessel. On the basis of these findings, we concluded that the cause of death was asphyxia resulting from airway obstruction compressed by the hematoma due to the arterial rupture. As the locality of the neurofibroma and hemorrhage were closed to the carotid baroreflex, we considered another possible mechanism of his sudden death, which could be cardiac inhibition induced by vagal stimulation. We hope this case will increase recognition of NF-1 vasculopathy when encountering any sudden death in NF1 patients.

Immune markers in the RASopathy neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a genetic disorder with an early mortality determined mostly by malignancy. Little is known about the immunosurveillance factors in NF1 patients. In this study we evaluated inflammatory markers and their cellular sources in NF1 patients to try understanding the relation of immune factors and the tumorigenesis that characterizes the disease. Using flow cytometry and ELISA, we assayed cytokines, co-stimulatory molecules, the functional state of circulating blood cells and cytokine plasma levels in a case-control transversal study. The frequency of CD4+ T cells seems reduced. In addition, a shift towards an anti-inflammatory profile was observed in cells expressing cytokines, except for a small subpopulation of CD8+ T cells that displayed an increased frequency of cells expressing the pro-inflammatory cytokine Tumor necrosis factor (TNF-α), while plasma soluble levels of Transforming growth factor-beta (TGF-β) and interleukin-6 (IL-6) were increased in NF1 patients. Knowledge of the regulation of NF1 and the role of TGF-beta signaling pathway in malignant peripheral nerve sheath tumor pathogenesis might shed light on molecular carcinogenesis mechanisms and lead to putative interventions both in prevention and treatment of malignant tumors.

A rare solitary neurofibroma of the frontal sinus

Neurofibromas are common peripheral nerve sheath tumors related to Schwann cell's proliferation and are usually associated with neurofibromatosis type 1. Although solitary neurofibroma that occurs in the paranasal sinus is reported occasionally, neurofibroma located in the frontal sinus is extremely rare. Here, we report a case of a young woman who had a heterogeneous lesion in the left frontal sinus, eroding its anterior and posterior wall with signs of intracranial invasion. Postoperatively, results of the histologic examination confirmed the diagnosis of solitary neurofibroma. In conclusion, solitary neurofibroma should be considered in the differential diagnosis of frontal sinus masses.

Induction of mitotic catastrophe by PKC inhibition in Nf1-deficient cells

Mutations of tumor suppressor Nf1 gene deregulate Ras-mediated signaling, which confers the predisposition for developing benign or malignant tumors. Inhibition of protein kinase C (PKC) was shown to be in synergy with aberrant Ras for the induction of apoptosis in various types of cancer cells. However, it has not been investigated whether loss of PKC is lethal for Nf1-deficient cells. In this study, using HMG (3-hydroxy-3-methylgutaryl, a PKC inhibitor), we demonstrate that the inhibition of PKC by HMG treatment triggered a persistently mitotic arrest, resulting in the occurrence of mitotic catastrophe in Nf1-deficient ST8814 cells. However, the introduction of the Nf1 effective domain gene into ST8814 cells abolished this mitotic crisis. In addition, HMG injection significantly attenuated the growth of the xenografted ST8814 tumors. Moreover, Chk1 was phosphorylated, accompanied with the persistent increase of cyclin B1 expression in HMG-treated ST8814 cells. The knockdown of Chk1 by the siRNA prevented the Nf1-deficient cells from undergoing HMG-mediated mitotic arrest as well as mitotic catastrophe. Thus, our data suggested that the suppression of PKC activates the Chk1-mediated mitotic exit checkpoint in Nf1-deficient cells, leading to the induction of apoptosis via mitotic catastrophe. Collectively, the study indicates that targeting PKC may be a potential option for developing new strategies to treat Nf1-deficiency-related diseases.

TAGLN expression is upregulated in NF1-associated malignant peripheral nerve sheath tumors by hypomethylation in its promoter and subpromoter regions

Neurofibromatosis type 1 (NF1) caused by NF1 gene mutation is a commonly inherited autosomal dominant disorder. Malignant peripheral nerve sheath tumors (MPNSTs), a type of aggressive sarcoma, are a major cause of mortality in NF1 patients. The malignant transformation of benign plexiform neurofibromas (PNs) to MPNSTs is a marked peculiarity in NF1 patients, yet the pathogenesis remains poorly understood. We found that an actin-associated protein transgelin (SM22) was highly expressed in NF1-deficient MPNST tissues compared to NF1-deficient PN tissues using immunohistological staining and primary cultured MPNST cells in western blot analysis. We further found that this transgelin upregulation was caused by increased transcriptional expression of the TAGLN gene encoding transgelin. Comparison of DNA methylation values in the promoter and subpromoter regions of the TAGLN gene in three types of NF1-deficient primary-cultured cells, derived from an NF1 patient's normal phenotype, a benign PN and MPNST tissues, revealed that the TAGLN gene was hypomethylated in the MPNST cells. Next, to determine the functional role of transgelin in MPNST pathogenesis, we manipulated the TAGLN gene expression and investigated the alteration of the RAS-mitogen-activated protein kinase (MAPK) signaling pathway in the normal-phenotypic and malignant tumor cells. The downregulation of TAGLN expression in NF1-deficient MPNST tumor cells through the treatment of the small interfering RNA resulted in a decrease in the RAS activation (GTP-RAS) and the downstream ERK1/2 activation (phosphorylated ERK1/2), while the overexpression of TAGLN in normal-phenotypic NF1-deficient cells caused an increase in RAS and ERK1/2 activation. These results indicate that upregulation of transgelin caused by hypomethylation of the TAGLN gene is closely involved in tumor progression in NF1.

Solitary giant neurofibroma of thigh

Neurofibromas are rare, benign, nerve sheath tumors in the peripheral nervous system. The solitary type is found in those who do not have neurofibromatosis. Solitary neurofibromas are too rare in the giant type. We report a rare case of a solitary giant neurofibroma of the anterior right thigh. The diagnostic criteria, characteristics of imaging studies, and operative approach are represented.

Gene expression profiling analysis reveals that DLG3 is down-regulated in glioblastoma

Glioblastoma multiforme (GBM) is the most malignant glioma. In the current study, 149 astrocytoma gene expression datasets were classified by prediction analysis of microarray. Strikingly, disks large homolog 3 (DLG3), a membrane-associated guanylate kinase-family gene, had the highest score in the GBM subset. DLG3 mRNA expression is significantly down-regulated in GBM relative to normal tissue and grade II or grade III astrocytoma according to the results of real-time polymerase chain reaction, and its protein expression shows an obvious difference by immunohistochemistry. Further assays show that DLG3 over-expression induces mitotic cell cycle arrest and apoptosis, and it inhibits proliferation and migration. However, DLG3 over-expression has almost no affect on invasion. The DLG3 protein expression in human brain GBM tissue and its effects on GBM cell invasion were not expected. Our data suggest that DLG3 is down-regulated in this cancer type. To our knowledge, this is the first report to clearly demonstrate the possible involvement of DLG3 in GBM.

Radiofrequency ablation and excision of multiple cutaneous lesions in neurofibromatosis type 1

Background

Von Recklinghausen disease or neurofibromatosis type 1 is an autosomal dominant genetic disorder of chromosome 17q11.2. The most common characteristic findings of NF 1 include multiple and recurrent cutaneous neurofibromas associated with psychosocial distress.

Methods

Sixteen patients (9 female, 7 male; average age, 31 years; range, 16 to 67 years) with multiple cutaneous neurofibromas between March 2010 and February 2012 were included in the study. All patients were treated with radiosurgical ablation and excision under general anesthesia.

Results

All 16 patients were satisfied with the results, when questioned directly during the outpatient department follow-up. The only complaint from a few patients was minimal scarring, but acceptable results were obtained in the end.

Conclusions

The radiofrequency procedure is almost bloodless and quick, creating a smaller necrotizing zone. Therefore, instead of employing the time consuming traditional surgery, such as laser therapy and electrosurgical excision, that produces uncertain results and can affect normal adjacent tissue, treatment of neurofibromas with radiofrequency ablation and excision can be an alternative choice of treatment for patients with a large number of neurofibromas.

NF1 deficiency causes Bcl-xL upregulation in Schwann cells derived from neurofibromatosis type 1-associated malignant peripheral nerve sheath tumors

Since the bi-allelic inactivation of both neurofibromin 1 (NF1) gene alleles (NF1(-/-)) in Schwann cells (SCs) is common in both benign plexiform neurofibromas (PNs) and malignant peripheral nerve sheath tumors (MPNSTs) in patients with neurofibromatosis type 1 (NF1), other genetic alterations in SCs may be required for tumor progression of PNs to MPNSTs. We found that the anti-apoptotic Bcl-xL protein is upregulated in MPNST tissues compared to PN tissues from patients with NF1 by immunohistological staining. In addition, we investigated whether Bcl-xL is upregulated in SCs derived from MPNSTs and found a significantly higher Bcl-xL expression level in sNF96.2 MPNST-derived SCs compared to normal human SCs (HSCs). We also discovered that the increased Bcl-xL expression caused an increase in drug resistance to doxorubicin in MPNST-derived SCs. Manipulation of NF1 gene expression levels by treatment with small interfering RNA (siRNA) and overexpression of the neurofibromin GAP-related domain (NF1-GRD) demonstrated that upregulated Bcl-xL expression in MPNST-derived SCs was caused by NF1 deficiency. Treatment with the Erk1/2 inhibitor, PD98059, resulted in a slight increase in Bcl-xL levels in neurofibromin-depleted normal HSCs, indicating that Bcl-xL upregulation in MPNST-derived SCs is mediated by activated Erk1/2, which is a Ras downstream protein regulated by neurofibromin. As the reduction of Bcl-xL expression restored sensitivity to doxorubicin-induced apoptosis in sNF96.2 cells, we examined the effect of the small molecule Bcl-xL inhibitor ABT-737 on sNF96.2 cells. A very low dose of ABT-737 combined with doxorubicin synergistically enhanced sensitivity to doxorubicin-induced apoptosis in sNF96.2 cells, suggesting that ABT-737 and doxorubicin may be a good combination to effectively treat NF1-associated MPNSTs with minimal side-effects. Collectively, our results suggest that upregulation of Bcl-xL in MPNST-derived SCs may be caused by the NF1 deficiency-mediated elevation in Ras/MAPK signaling and may provide a new potential chemotherapeutic target in patients with NF1 and MPNSTs.

Molecular heterogeneity in malignant peripheral nerve sheath tumors associated with neurofibromatosis type 1

Neurofibromatosis type-1 (NF1), resulting from NF1 gene loss of function, is characterized by an increased risk of developing benign and malignant peripheral nerve sheath tumors (MPNSTs). Whereas the cellular heterogeneity of NF1-associated tumors has been well studied, the molecular heterogeneity of MPNSTs is still poorly understood. Mutational heterogeneity within these malignant tumors greatly complicates the study of the underlying mechanisms of tumorigenesis. We have explored this molecular heterogeneity by performing loss of heterozygosity (LOH) analysis of the NF1, TP53, RB1, PTEN, and CDKN2A genes on sections of 10 MPNSTs derived from 10 unrelated NF1 patients. LOH data for the TP53 gene was found to correlate with the results of p53 immunohistochemical analysis in the same tumor sections. Further, approximately 70% of MPNSTs were found to display intra-tumoral molecular heterogeneity as evidenced by differences in the level of LOH between different sections of the same tumor samples. This study constitutes the first systematic analysis of molecular heterogeneity within MPNSTs derived from NF1 patients. Appreciation of the existence of molecular heterogeneity in NF1-associated tumors is important not only for optimizing somatic mutation detection, but also for understanding the mechanisms of NF1 tumorigenesis, a prerequisite for the development of specifically targeted cancer therapeutics.

Assessment of the potential pathogenicity of missense mutations identified in the GTPase-activating protein (GAP)-related domain of the neurofibromatosis type-1 (NF1) gene

Neurofibromatosis type-1 (NF1) is caused by constitutional mutations of the NF1 tumor-suppressor gene. Although ∼85% of inherited NF1 microlesions constitute truncating mutations, the remaining ∼15% are missense mutations whose pathological relevance is often unclear. The GTPase-activating protein-related domain (GRD) of the NF1-encoded protein, neurofibromin, serves to define its major function as a negative regulator of the Ras-MAPK (mitogen-activated protein kinase) signaling pathway. We have established a functional assay to assess the potential pathogenicity of 15 constitutional nonsynonymous NF1 missense mutations (11 novel and 4 previously reported but not functionally characterized) identified in the NF1-GRD (p.R1204G, p.R1204W, p.R1276Q, p.L1301R, p.I1307V, p.T1324N, p.E1327G, p.Q1336R, p.E1356G, p.R1391G, p.V1398D, p.K1409E, p.P1412R, p.K1436Q, p.S1463F). Individual mutations were introduced into an NF1-GRD expression vector and activated Ras was assayed by an enzyme-linked immunosorbent assay (ELISA). Ten NF1-GRD variants were deemed to be potentially pathogenic by virtue of significantly elevated levels of activated GTP-bound Ras in comparison to wild-type NF1 protein. The remaining five NF1-GRD variants were deemed less likely to be of pathological significance as they exhibited similar levels of activated Ras to the wild-type protein. These conclusions received broad support from both bioinformatic analysis and molecular modeling and serve to improve our understanding of NF1-GRD structure and function.

Neurogenic tumors of soft tissue

Neurogenic tumors are an uncommon yet important category of soft tissue tumors in children and adolescents because of their frequent association with various genetic syndromes. The heterogeneous cellular composition of the peripheral nerve and the wide metaplastic capacity of the neural crest and its derivatives generate a variety of neoplasms with neurogenic differentiation. This article reviews the clinicopathologic features and differential diagnosis of neurogenic tumors in the first two decades of life, and highlights use of selected ancillary methods for diagnosis.

Neurofibromatosis type 1-associated tumours: their somatic mutational spectrum and pathogenesis

Somatic gene mutations constitute key events in the malignant transformation of human cells. Somatic mutation can either actively speed up the growth of tumour cells or relax the growth constraints normally imposed upon them, thereby conferring a selective (proliferative) advantage at the cellular level. Neurofibromatosis type-1 (NF1) affects 1/3,000-4,000 individuals worldwide and is caused by the inactivation of the NF1 tumour suppressor gene, which encodes the protein neurofibromin. Consistent with Knudson's two-hit hypothesis, NF1 patients harbouring a heterozygous germline NF1 mutation develop neurofibromas upon somatic mutation of the second, wild-type, NF1 allele. While the identification of somatic mutations in NF1 patients has always been problematic on account of the extensive cellular heterogeneity manifested by neurofibromas, the classification of NF1 somatic mutations is a prerequisite for understanding the complex molecular mechanisms underlying NF1 tumorigenesis. Here, the known somatic mutational spectrum for the NF1 gene in a range of NF1-associated neoplasms --including peripheral nerve sheath tumours (neurofibromas), malignant peripheral nerve sheath tumours, gastrointestinal stromal tumours, gastric carcinoid, juvenile myelomonocytic leukaemia, glomus tumours, astrocytomas and phaeochromocytomas -- have been collated and analysed.

Neoplasms associated with germline and somatic NF1 gene mutations

INTRODUCTION

Neurofibromatosis 1 is a tumor predisposition genetic syndrome with autosomal dominant inheritance and virtually 100% penetrance by the age of 5 years. NF1 results from a loss-of-function mutation in the NF1 gene, resulting in decreased levels of neurofibromin in the cell. Neurofibromin is a negative regulator of various intracellular signaling pathways involved in the cellular proliferation. Although the loss of heterozygosity in the NF1 gene may predispose NF1 patients to certain malignancies, additional genetic alterations are a prerequisite for their development. The precise nature of these additional genetic alterations is not well defined, and genetic testing of all malignancies in NF1 patients becomes an essential component of future research in this subset of patients. In addition to germline NF1 mutations, alteration of the somatic NF1 gene is associated with sporadic malignancies such as adenocarcinoma of the colon, myelodysplastic syndrome, and anaplastic astrocytoma.

MATERIALS AND METHODS

A comprehensive English and non-English language search for all articles pertinent to malignancies associated with NF1 was conducted using PubMed, a search engine provided by the U.S. National Library of Medicine and the National Institutes of Health. Key words searched included the following: "malignancies associated with NF1", "tumors associated with NF1", and "NF1 and malignancies". A comprehensive analysis in terms age and mode of presentation, investigation and therapeutic modalities, and outcome of the published data was performed and compared with similar information on the sporadic cases.

RESULTS

Malignancies in NF1 patients typically occur at an earlier age and, with an exception of optic pathway gliomas, certain types of malignancies carry a poor prognosis compared with their sporadic counterparts. Malignancies are the leading cause of death in NF1 patients, resulting in a 10- to 15-year decreased life expectancy compared with the general population.

CONCLUSIONS

The lack of well-defined screening tests for early detection and the nonspecific clinical presentation contributes to a poorer outcome in malignancies associated with NF1. Small study group size, mixed patient population, and a lack of uniformity in reporting research results make comparison of treatment outcome for this group difficult. An International Consensus Meeting to address and recommend best practices for screening, diagnosis, management, and follow-up of malignancies associated with NF1 is needed.

Glioblastoma biomarkers from bench to bedside: advances and challenges

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumour, with few available therapies providing significant improvements in mortality. Biomarkers, which are defined by the National Institutes of Health as 'characteristics that are objectively measured and evaluated as indicators of normal biologic processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention', have the potential to play valuable roles in the diagnosis and treatment of GBM. Although GBM biomarker research is still in its early stages because of the tumour's complex pathophysiology, a number of potential markers have been identified which can be measured in either brain tissue or blood serum. In conjunction with other clinical data, particularly neuroimaging modalities such as MRI, these proteins could contribute to the clinical management of GBM by helping to classify tumours, predict prognosis and assess treatment response. In this article, we review the current understanding of GBM pathophysiology and recent advances in GBM biomarker research, and discuss the potential clinical implications of promising biomarkers. A better understanding of GBM pathophysiology will allow researchers and clinicians to identify optimal biomarkers and methods of interpretation, leading to advances in tumour classification, prognosis prediction and treatment assessment.

Exploring the somatic NF1 mutational spectrum associated with NF1 cutaneous neurofibromas

Neurofibromatosis type-1 (NF1), caused by heterozygous inactivation of the NF1 tumour suppressor gene, is associated with the development of benign and malignant peripheral nerve sheath tumours (MPNSTs). Although numerous germline NF1 mutations have been identified, relatively few somatic NF1 mutations have been described in neurofibromas. Here we have screened 109 cutaneous neurofibromas, excised from 46 unrelated NF1 patients, for somatic NF1 mutations. NF1 mutation screening (involving loss-of-heterozygosity (LOH) analysis, multiplex ligation-dependent probe amplification and DNA sequencing) identified 77 somatic NF1 point mutations, of which 53 were novel. LOH spanning the NF1 gene region was evident in 25 neurofibromas, but in contrast to previous data from MPNSTs, it was absent at the TP53, CDKN2A and RB1 gene loci. Analysis of DNA/RNA from neurofibroma-derived Schwann cell cultures revealed NF1 mutations in four tumours whose presence had been overlooked in the tumour DNA. Bioinformatics analysis suggested that four of seven novel somatic NF1 missense mutations (p.A330T, p.Q519P, p.A776T, p.S1463F) could be of functional/clinical significance. Functional analysis confirmed this prediction for p.S1463F, located within the GTPase-activating protein-related domain, as this mutation resulted in a 150-fold increase in activated GTP-bound Ras. Comparison of the relative frequencies of the different types of somatic NF1 mutation observed with those of their previously reported germline counterparts revealed significant (P=0.001) differences. Although non-identical somatic mutations involving either the same or adjacent nucleotides were identified in three pairs of tumours from the same patients (P<0.0002), no association was noted between the type of germline and somatic NF1 lesion within the same individual.

S100B and neurofibromin immunostaining and X-inactivation patterns of laser-microdissected cells indicate a multicellular origin of some NF1-associated neurofibromas

Neurofibromatosis 1 (NF1) is an autosomal dominant disease that predisposes individuals to developing benign neurofibromas. Some features and consequences of NF1 appear to result from partial deficiency of neurofibromin (Nfn), the NF1 gene protein product, as a result of haploinsufficiency for the NF1 gene. Other features and consequences of NF1 appear to involve total deficiency of Nfn, which arises as a result of either loss of function of the second NF1 allele or excess degradation of Nfn produced by the second allele in a particular clone of cells. We used immunofluorescence to assess the presence of Nfn in putative Schwann cells (S100B(+) ) and non-Schwann cells (S100B(-) ) in 36 NF1-derived benign neurofibromas classified histologically as diffuse or encapsulated. The S100B(+) /Nfn(-) cell population made up only 18% ± 10% (mean ± standard deviation) of the neurofibroma cells in both the diffuse and encapsulated neurofibromas. The proportion of S100B(+) /Nfn(+) cells was significantly higher and the proportion of S100B(-) /Nfn(-) cells was significantly lower in diffuse neurofibromas than in encapsulated neurofibromas. We isolated S100B(+) /Nfn(+) , S100B(+) /Nfn(-) , and S100B(-) /Nfn(+) cells by laser microdissection and, using X-chromosome inactivation profiles, assessed clonality for each cell type. We showed that, although some neurofibromas include a subpopulation of S100B(+) /Nfn(-) cells consistent with clonal expansion of a Schwann cell progenitor that has lost function of both NF1 alleles, other neurofibromas do not show evidence of monoclonal proliferation of Schwann cells. Our findings suggest that, although clonal loss of neurofibromin function is probably involved in the development of some NF1-associated neurofibromas, other pathogenic processes also occur.

Analysis of NF1 somatic mutations in cutaneous neurofibromas from patients with high tumor burden

Neurofibromatosis type 1, (NF1) is a complex, autosomal dominant disorder characterized by benign and malignant tumors which result from NF1 gene mutations. The molecular mechanisms that underlie NF1 tumorigenesis are still poorly understood although inactivation of other modifying loci in conjunction with NF1 mutations is postulated to be involved. These modifying loci may include deficiencies in mismatch repair genes and elements involved in cell cycle regulation (TP53, RB1, and CDKN2A). We have analyzed the somatic mutations in 89 cutaneous neurofibromas derived from three unrelated NF1 patients with high tumor burden, by loss of heterozygosity (LOH) analysis of the NF1, TP53, RB1, and CDKN2A genes, by assessing microsatellite instability (MSI), by direct sequencing of the NF1, TP53, and several mismatch repair (MMR) genes and by multiplex ligation-dependent probe amplification of the NF1 and TP53 genes. The aim was both to assess the possible clonality of these tumors and also to assess the involvement of other potential genetic loci in the development of these neurofibromas. Somatic NF1 mutations were identified in 57 (64%) of neurofibroma samples. Each mutation was distinct demonstrating the independent origin of each tumor. While somatic LOH of the TP53 gene was identified in four tumors, no specific deletions or sequence variations were identified. LOH of markers flanking the RB1 gene was also found in one tumor but no CDKN2A mutations were detected. Although evidence of MSI was seen in 21 tumors, no MMR gene alterations were identified. The identification of LOH involving TP53 and RB1 loci is a novel finding in benign cutaneous neurofibromas possibly demonstrating an alternative underlying molecular mechanism associated with the development of these benign tumors from this cohort of patients.

Neurofibromatosis Type 1 and tumorigenesis: molecular mechanisms and therapeutic implications

Neurofibromatosis Type 1 (NF1) is a common autosomal dominant disease characterized by complex and multicellular neurofibroma tumors, and less frequently by malignant peripheral nerve sheath tumors (MPNSTs) and optic nerve gliomas. Significant advances have been made in elucidating the cellular, genetic, and molecular biology involved in tumor formation in NF1. Neurofibromatosis Type 1 is caused by germline mutations of the NF1 tumor suppressor gene, which generally result in decreased intracellular neurofibromin protein levels, leading to increased cascade Ras signaling to its downstream effectors. Multiple key pathways are involved with the development of tumors in NF1, including Ras/mitogen-activated protein kinase (MAPK) and Akt/mammalian target of rapamycin (mTOR). Interestingly, recent studies demonstrate that multiple other developmental syndromes (in addition to NF1) share phenotypic features resulting from germline mutations in genes responsible for components of the Ras/MAPK pathway. In general, a somatic loss of the second NF1 allele, also referred to as loss of heterozygosity, in the progenitor cell, either the Schwann cell or its precursor, combined with haploinsufficiency in multiple supporting cells is required for tumor formation. Importantly, a complex series of interactions with these other cell types in neurofibroma tumorigenesis is mediated by abnormal expression of growth factors and their receptors and modification of gene expression, a key example of which is the process of recruitment and involvement of the NF1+/– heterozygous mast cell. In general, for malignant transformation to occur, there must be accumulation of additional mutations of multiple genes including INK4A/ARF and P53, with resulting abnormalities of their respective signal cascades. Further, abnormalities of the NF1 gene and molecular cascade described above have been implicated in the tumorigenesis of NF1 and some sporadically occurring gliomas, and thus, these treatment options may have wider applicability. Finally, increased knowledge of molecular and cellular mechanisms involved with NF1 tumorigenesis has led to multiple preclinical and clinical studies of targeted therapy, including the mTOR inhibitor rapamycin, which is demonstrating promising preclinical results for treatment of MPNSTs and gliomas.

Cytogenetics of neurofibromas: two case reports and literature review

Only a few karyotypes of neurofibromas have been documented in the literature. In this report, we describe two new cases in which conventional cytogenetics demonstrated the presence of abnormal clones. Combining karyotypes of the nine previously reported cases, we found that the most frequent structural rearrangements involved chromosome 9p. Including the two cases reported here, 5/11 cases involved 9p, and four of these involved the 9p21 approximately p22 region.

Synchronous meningioma and anaplastic large cell lymphoma

Synchronous primary brain tumors are exceedingly rare. When they occur, most cases are associated with metastatic disease. To the best of our knowledge, we report the first case of an atypical meningioma infiltrated by a T-cell-primary central nervous system lymphoma (PCNSL), specifically anaplastic large cell lymphoma (ALCL). We present a novel, unifying, plausible mechanism for its origin based on theories in the current literature. A 65-year-old man with a history of near-total resection of atypical meningioma presented with a complaint of progressive headaches. Imaging revealed recurrent tumor. Left frontal-temporal craniotomy with near-total tumor resection followed by radiation was performed. Recurrent symptomatic tumor led to repeat left frontotemporal craniotomy with tumor resection and partial anterior temporal lobectomy. Part of the specimen showed predominantly fibrotic neoplasm composed of nests and whorls of meningothelial cells, highlighted by epithelial membrane antigen (EMA) staining. The remainder of the specimen consisted of densely cellular neoplasm centered in connective tissue, including areas involved by meningioma. This tumor was composed of moderately large lymphoid cells with large nuclei, prominent nucleoli, and amphophilic cytoplasm. These cells were strongly immunoreactive for CD3 and CD30 but remained unstained with EMA, anaplastic lymphoma kinase-1 (ALK-1), CD15 or cytotoxic associated antigen TIA-1. Smaller mature lymphocytes, chiefly T-cells, were intermixed. The morphologic and immunohistochemical features were considered typical of anaplastic large T-cell lymphoma. The pathogenesis of this association may have been due to radiation-mediated breakdown of the blood-brain barrier with subsequent T-cell infiltration and proliferation. We advocate aggressive resection and long-term surveillance for individuals with metastasis, especially higher-grade neoplasms that receive radiotherapy.

Localized, plexiform, diffuse, and other variants of neurofibroma in 12 dogs, 2 horses, and a chicken

In humans, neurofibroma and schwannoma are distinct entities within the group of benign peripheral nerve sheath tumors. In the veterinary literature, these tumors are often classified together simply as benign peripheral nerve sheath tumors, and diagnostic criteria for their subclassification are not well established. We describe peripheral nerve sheath tumors with microscopic, immunohistologic, and ultrastructural features similar to those in subtypes of human neurofibroma in 12 dogs, 2 horses, and 1 chicken. Dogs were of different breeds and were aged 2 months to 15 years. The canine tumors were located in the skin, peripheral nerve, tongue, and large intestine. The 2 horses were 11 and 12 years old. The equine tumors were located in the subcutis of the neck and axilla. The chicken was a mature white Leghorn chicken with an ocular neoplasm. Neurofibromas of this study had localized, plexiform, diffuse and combined plexiform and diffuse growth patterns, and microscopic features similar to those in classic, collagenous, cellular, myxoid, and pigmented neurofibromas of humans. One diffuse neurofibroma contained areas of schwannian differentiation (hybrid neurofibroma-schwannoma). Two plexiform neurofibromas occurred together with diffuse ganglioneuromatosis in the large intestine of young dogs, as has also been reported in humans. This investigation shows the existence of identical subtypes of neurofibroma in animals and humans and identifies similarities in tumor location and patient age between animals and humans. This report will allow a more discriminating classification of benign peripheral nerve sheath tumors and probably has a bearing on epidemiology, pathogenesis and prognosis.

Germline and somatic NF1 gene mutation spectrum in NF1-associated malignant peripheral nerve sheath tumors (MPNSTs)

About 10% of neurofibromatosis type 1 (NF1) patients develop malignant peripheral nerve sheath tumors (MPNSTs) and represent considerable patient morbidity and mortality. Elucidation of the genetic mechanisms by which inherited and acquired NF1 disease gene variants lead to MPNST development is important. A study was undertaken to identify the constitutional and somatic NF1 mutations in 34 MPNSTs from 27 NF1 patients. The NF1 germline mutations identified in 22 lymphocytes DNA from these patients included seven novel mutations and a large 1.4-Mb deletion. The NF1 germline mutation spectrum was similar to that previously identified in adult NF1 patients without MPNST. Somatic NF1 mutations were identified in tumor DNA from 31 out of 34 MPNSTs, of which 28 were large genomic deletions. The high prevalence (>90%) of such deletions in MPNST contrast with the =or<20% found in benign neurofibromas and is indicative of the involvement of different mutational mechanisms in these tumors. Coinactivation of the TP53 gene by deletion, or by point mutation along with NF1 gene inactivation, is known to exacerbate disease symptoms in NF1, therefore TP53 gene inactivation was screened. DNA from 20 tumors showed evidence for loss of heterozygosity (LOH) across the TP53 region in 11 samples, with novel TP53 point mutations in four tumors.

Non-excision treatment of multiple cutaneous neurofibromas by laser photocoagulation

Neurofibromatosis type 1 (NF-1) is an autosomal dominant disorder characterized by skin tumours derived from peripheral nerves. It is a clinically diagnosed disorder of a mainly cosmetic concern. There are different excision modalities for treatment of cutaneous neurofibromas; however, none is considered to be universally accepted treatment. This study was conducted to evaluate a non-excision treatment of multiple cutaneous neurofibromas, using surface and interstitial approaches of neodymium:yttrium aluminum garnet (Nd:YAG) laser (1,064 nm) photocoagulation, depending upon the size and location of the lesions. Twelve patients with multiple cutaneous neurofibromas were included. Surface laser photocoagulation by long-pulsed Nd:YAG laser has been used for treatment of flat lesions, while interstitial laser photocoagulation by continuous wave (CW) Nd:YAG laser has been used for treatment of bulkier lesions. After 14 months of follow up, both approaches of laser photocoagulation have shown different success rates, as denoted by the regression of the lesions, an overall acceptable cosmetic outcome, and, generally, patients' satisfaction. Within the limitations of the present study, laser photocoagulation has proven to be a promising technique that may be an alternative or additive modality for treatment of multiple cutaneous neurofibromas. It is a minimally invasive, office-based technique that could be used safely and effectively, with a limited rate of complications. Surface laser photocoagulation has proven to be an effective tool for treatment of flat lesions, especially those located in exposed areas, with a favourable cosmetic result, while interstitial laser photocoagulation could be reserved for bulkier lesions, especially those located in non-exposed areas. However, further studies are necessary to refine the procedure, and to confirm the present encouraging findings, especially over a longer period of follow up, as well as to evaluate laser parameters for optimization of the technique.

Recurrent massive subcutaneous hemorrhage in neurofibromatosis type 1: a case report

Neurofibromatosis type 1 (NF-1) is an autosomal dominant disorder that has three major features: multiple neural tumors, cafe-au-lait spots, and pigmented iris hamartomas (Lisch nodules). The purpose of this case report is to advise physicians of the danger associated with the progression of fast-onset massive hemorrhage to hemodynamic instability, which mandates rapid treatment to prevent the development of a life-threatening condition. A 64-yr-old woman with NF-1 was admitted to the Emergency Department (ED) because of a rapidly growing, 10 x 5 x 3 cm-sized mass on the left back area. She had previously undergone surgery for a large subcutaneous hematoma, which had developed on her right back area 30 yr before. She became hemodynamically unstable with hypotension during the next 3 hr after admission to ED. Resuscitation and blood transfusion were done, and the hematoma was surgically removed. The mass presented as a subcutaneous, massive hematoma with pathologic findings of neurofibroma. We report a case of NF-1 that presented as recurrent, massive, subcutaneous hemorrhage on the back region combined with hypovolemic shock.

Forensic considerations in cases of neurofibromatosis--an overview

Neurofibromatosis types 1 and 2 are inherited neurocutaneous disorders characterized by a variety of manifestations that involve the circulatory system, the central and peripheral nervous systems, the skin, and the skeleton. Significant reduction in lifespan occurs in both conditions often related to complications of malignancy and hypertension. Individuals with these conditions may also be the subject of medicolegal autopsy investigation if sudden death occurs. Unexpected lethal events may be associated with intracranial neoplasia and hemorrhage or brainstem compression. Vasculopathy with fibrointimal proliferation may result in critical reduction in blood flow within the coronary or cerebral circulations, and aneurysmal dilatation may be associated with rupture and life-threatening hemorrhage. An autopsy approach to potential cases should include review of the history/hospital record, liaison with a clinical geneticist (to include family follow-up), a full external examination with careful documentation of skin lesions and nodules, measurement of the head circumference in children, photography, possible radiologic examination, a standard internal autopsy examination, documentation of the effects of previous surgery and/or chemo/radiotherapy, examination for specific tumors, specific examination and sampling of vasculature (renal, cerebral, and cardiac), formal neuropathologic examination of brain and spinal cord, possible examination of the eyeballs, examination of the gastrointestinal tract, histology to include tumors, vessels, gut, and bone marrow, toxicological testing for anticonvulsants, and sampling of blood and tissue for possible cytogenetic/molecular evaluation if required.

Experimental therapeutic approaches to peripheral nerve tumors

✓Discovery that the Schwann cell is the primary cell type responsible for both the neurofibroma as well as the schwannoma has proven to represent a crucial milestone in understanding the pathogenesis of peripheral nerve tumor development. This information and related findings have served as a nidus for research aimed at more fully characterizing this family of conditions. Recent discoveries in the laboratory have clarified an understanding of the molecular mechanisms underlying the pathogenesis of benign peripheral nerve tumors. Similarly, the mechanisms whereby idiopathic and syndromic (NF1- andNF2-associated) nerve sheath tumors progress to malignancy are being elucidated. This detailed understanding of the molecular pathogenesis of peripheral nerve tumors provides the information necessary to create a new generation of therapies tailored specifically to the prevention, cessation, or reversal of pathological conditions at the fundamental level of dysfunction. The authors review the data that have helped to elucidate the molecular pathogenesis of this category of conditions, explore the current progress toward exploitation of these findings, and discuss potential therapeutic avenues for future research.

A brief history of surgery for peripheral nerve sheath tumors

✓The authors present a brief and selective history of surgery for peripheral nerve tumors to illustrate how the current understanding of the nature of disease influences the choice of surgical intervention. There was very little understanding of the anatomy and function of peripheral nerves in ancient times; consequently, surgical treatments for peripheral nerve tumors were based on the writings of authorities. The confusion between traumatic neuromas and genuine nerve sheath tumors coupled with the belief that manipulation of a peripheral nerve might be lethal to the patient stifled the development of surgical techniques for the management of nerve tumors in the 18th and 19th centuries. It was not until the 20th century, with an increased understanding of the microscopic anatomy of nerve sheath tumors, that efficacious surgical treatments for these diseases were developed. Continued advances in the understanding of the biology of these tumors will continue to impact their surgical management.

Tumors of the brachial plexus

✓Tumors of the brachial plexus are relatively rare and present a clinical challenge for the neurosurgeon. The management of these tumors therefore requires not only an understanding of the complex anatomy of the brachial plexus but also an appreciation of the appropriate surgical approach to the various tumors that may be encountered. Over a 30-year period (1969–1999), 226 patients with brachial plexus tumors were evaluated and surgically treated by the senior authors (R.L.T., D.G.K.). In the present paper they review the most common benign and malignant brachial plexus tumors and discuss management and surgical principles established through their experience at the Louisiana State University Health Sciences Center.

Characterization of plasma protein profiles from patients with neurofibromatosis I

BACKGROUND

Neurofibromatosis type I (NF1) is a common autosomal dominant disorder, affecting approximately one in every 3500 individuals. Early diagnosis of NF1 can be ambiguous, and clinical symptoms are diverse. We compared plasma protein profiles between normal controls and NF1 patients for yielding important insights into the mechanisms underlying NF1 related tumor formation and diagnostic biomarkers to classify the diverse clinical symptoms.

METHODS

MALDI-TOF mass spectrometry was used to identify plasma proteins. Prior to that, a micro-solution isoelectric focusing (microsol-IEF) pre-fractionation combined with two-dimensional gel electrophoresis (2-DE) using the narrow pH range strip was applied to enhance the resolution and sensitivity.

RESULTS

There was a significant increase in fibrinogen level in patients with NF1. This increase in fibrinogen expression was subsequently confirmed by Western blotting assay. Furthermore, the effect of fibrinogen on cell growth was tested on PC12 cells.

CONCLUSION

Fibrinogen is the central protein associated with angiogenesis; a process which modulates tumor growth, the up-regulation of fibrinogen may help explain the development of neurofibromas in NF1 patients.

Hitting the mark in hamartoma syndromes

The missed mark or hamartia underlying each hamartoma syndrome is a mutation in a tumor suppressor gene. This sets the stage for the development of frequent and early tumors in multiple organs. Loss of function of the tumor suppressor in neoplastic cells leads to dysregulation of signaling pathways and tumor growth. The convergence of these signaling pathways to the mTOR pathway suggests that rapamycin or rapamycin-like drugs have potential for treatment, perhaps in combination with drugs targeting other signaling pathways. Haploinsufficient cells also play significant roles in tumor formation. Disrupting interactions between neoplastic cells and surrounding haploinsufficient cells using antiangiogenesis therapies represent an additional approach for treatment. It is hoped that the debilitating effects of these syndromes soon will be alleviated or even reversed though targeted therapies.

Induction of melanocytes from embryonic stem cells and their therapeutic potential

Embryonic stem (ES) cells from many organisms have the capacity to generate in vitro a wide variety of cell types depending on their environment. Understanding precisely how such toti- or pluripotent cells may be driven towards a specific lineage represents a major challenge if our ambition of using ES cells to generate a ready supply of healthy cells for cell-based therapies for a range of diseases is to be realized. Recent advances have demonstrated that melanocytes and retinal pigmented epithelial (RPE) cells exhibiting the characteristics of their natural counterparts can be induced from undifferentiated ES cells grown on monolayers of specific stromal cell lines or by using a combination of Wnt3a, Endothelin-3 and SCF. The ability to induce pigment cells from ES cells promises to facilitate our understanding of the precise molecular mechanisms underlying this process and moreover enable us to distinguish the program of gene expression that underpins the choice made between generating a nerual crest-type melanocyte versus an RPE cell. Moreover, once the combination of signals required to induce a particular type of pigment cell are characterized, the way may be open for future cell-based therapy for various diseases caused by defective pigment cells.