Diverse differentiation in malignant peripheral nerve sheath tumours associated with neurofibromatosis-1: an immunohistochemical and ultrastructural study

Immunohistochemical Distinguishing between Canine Peripheral Nerve Sheath Tumors and Perivascular Wall Tumors

Peripheral nerve sheath tumors (PNSTs) comprise a heterogeneous group of neoplasms originating from the elements of the nerve sheath. They are divided into two forms: benign and malignant PNST. Both benign and malignant PNSTs are not very common in domestic animals but they are reported in different animal species. Histologically, PNSTs are composed predominantly of spindle cells arranged in bundles, whorls and sheets, with a different number of pleomorphic cells and mitotic figures.

The aim of this study was a reclassification of 17 dog tumor samples initially diagnosed with peripheral nerve sheath tumors using histopathological analysis. The main criterion for reclassification was immunohistochemical positivity for various antigens.

PNSTs are often histologically very similar to other spindle cell tumors and immunohistochemistry is required for differential diagnosis. PNSTs generally express vimentin, S-100 protein, glial fibrillary acidic protein (GFAP), collagen IV and laminin.

Four tumor samples were positive to muscular marker α-SMA and vimentin and negative for S-100 protein and desmin. The spindle cells whirling around some blood vessels were observed in these tumors so they were reclassified as perivascular wall tumors (PWTs). The other 13 tumors were S-100 protein and vimentin positive and α-SMA and desmin negative, thus classified as PNST.

The use of the immunohistochemical panel is necessary for distinguishing PNSTs from PWTs in routine diagnostics.

Malignant peripheral nerve sheath tumours and neurofibromatosis 1: A case series and recommendations for care

Background: The incidence of malignant peripheral nerve sheath tumours (MPNST) in patients with neurofibromatosis 1 (NF1) is significantly higher than that of the general population. NF1-associated MPNST occur at a younger age and carry a worse prognosis than sporadic MPNST.Aim: This case series describes four cases of MPNST in patients with NF1.Setting: The study was performed in a public academic hospital in the Western Cape province of South Africa.Method: Demographics, disease status, histopathology, treatment and outcome data were collected retrospectively from medical charts and through review of histological slides.Results: The median age was 36.5 years. All tumours were > 5 cm at presentation and located on the trunk. One patient presented with metastatic disease. There was a mean delay of 3.5 months from presentation to initiation of treatment. Three patients underwent wide excision, with one receiving adjuvant chemotherapy and radiotherapy. At a median follow-up of 20 months from histological diagnosis only one patient was alive in clinical remission. Two patients had succumbed to progressive disease at 8 and 16 months from diagnosis and one patient with terminal metastatic disease was lost to follow-up.Conclusion: In this series the patients presented with advanced, often unresectable lesions for which single modality therapy was not curative. An adult NF1 health surveillance guideline for resource-constrained environments could lead to early diagnosis and treatment of MPNST and other complications in NF1 patients.

Oncolytic measles virus as a novel therapy for malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are devastating soft tissue sarcomas that can arise sporadically or in association with neurofibromatosis type I, have a poor prognosis, and have limited treatment options. Oncolytic measles virus therapy has been demonstrated to have significant antitumor properties in a number of different cancers, but the oncolytic potential of a MV Edmonston (MVEdm) vaccine strain engineered to express the human sodium iodide symporter (MV-NIS) on MPNST has not previously been evaluated. MPNST cell lines were found to highly express CD46, a cellular receptor required for measles viral entry, on their cell surface. After in vitro MV-NIS infection, MPNST cell lines showed significant cytopathic effect (CPE), while normal Schwann cells were less susceptible to CPE. Virus localization and distribution could be monitored by imaging of I-125 uptake. Local administration of MV-NIS into MPNST-derived tumors resulted in significant regression of tumor and improved survival. These results demonstrate feasibility of oncolytic measles virus therapy for MPNST patients and the possibility of a novel treatment for patients with NF1 tumors.

Ulnar malignant peripheral nerve sheath tumour diagnosis in a mixed-breed dog as a model to study human: histologic, immunohistochemical, and clinicopathologic study

Canine Malignant Peripheral Nerve Sheath Tumors (MPNSTs) are uncommonly reported in the ulnar, since they are underestimated relative to the more common spindle cell tumours of soft tissue. In dogs, MPNST accounts for 27% of nervous system tumours. In man, MPNST represents 5-10% of all soft tissue sarcomas and is often associated with neurofibromatosis type 1 (NF-1).An 8-year-old, 9 kg, female mixed-breed dog with a subcutaneous mass on the upper right side of the ulnar region was presented to the small animal research and teaching hospital of Tehran University. The dog was anorexic with general weakness. The mass (7 × 4 cm) was removed surgically and processed routinely. Microscopically, the mass was composed of highly cellular areas with a homogeneous population of round or spindle cells, high cellular pleomorphism, high mitotic index and various morphologic patterns. Furthermore, spindle cells arranged in densely or loosely sweeping fascicles, interlacing whorls, or storiform patterns together with wavy cytoplasm, nuclear palisades, and round cells were arranged in sheets or cords with a meshwork of intratumoral nerve fibers. In addition, in this case the presence of neoplastic cells within the blood vessels was observed. Immunohistochemically, tumor was positive for vimentin and S-100 protein. The histopathologic features coupled with the S-100 and vimentin immunoreactivity led to a diagnosis of malignant neurofibroma.

To the best of our knowledge, primary ulnar MPNST has not been reported in animals. This is the first documentation of an ulnar malignant peripheral nerve sheath tumour in a dog.

Feline cutaneous nerve sheath tumours: histological features and immunohistochemical evaluations

Feline cutaneous nerve sheath tumours (CNSTs) are uncommonly reported in the skin, since they are underestimated relative to the more common spindle cell tumours of soft tissue. In this study, 26 nerve sheath tumours selected from 337 skin neoplasms of cats were examined. Histologically, they were classified into malignant (MPNSTs) and benign tumours (BPNSTs) based on degree of cellular atypia and polymorphism as well as mitotic rate and diffuse necrosis. CPNSTs were tipically characterised by Antoni A pattern, in some cases associated with Antoni B pattern. In the malignant peripheral nerve sheath tumours (MPNSTs) the polymorphism was marked, while it was mild to moderate in the benign forms (BPNSTs). In the MPNSTs the mitotic activity was generally higher than in the BPNSTs. In five cases, including three MPNSTs and two BPNSTs, there were multinucleated giant cells. Necrotic foci occurred in a BPNST and in two MPNSTs, while osseous/chondroid metaplasia was found in two cases. Immunohistochemically, all the tumours showed a marked diffuse vimentin expression. S-100 protein was expressed in 17 cases, including 81.8% of BPNSTs and 57.14% of MPNSTs. Twenty-five tumours expressed NSE and twenty-four cases showed immunoreaction for laminin. Thirteen tumours were positive for GFAP, while five tumours were positive for SMA. PGP 9.5 expression was detected in all cases, except for two MPNSTs. NGFR was expressed in eleven cases, including four MPNSTs and seven BPNSTs. Ki67 was expressed in twenty tumours without any relationship with morphologic malignancy of the neoplasm. In this case series we confirmed neoplastic spindloid cells with wavy cytoplasm arranged in compact areas, with occasional nuclear palisading or whirls, and interchanged with loosely arranged areas, as the morphological features supporting a diagnosis of CPNST. A constant concurrent expression of vimentin, NSE, and laminin might confirm the diagnosis of PNST in the absence of clear S-100 protein positivity, especially in the malignant forms. In this study, conclusive data were not obtained on the diagnostic relevance of NGFR- and PGP 9.5-expression in feline CPNSTs.

Malignant peripheral nerve sheath tumors: differentiation patterns and immunohistochemical features - a mini-review and our new findings

Malignant peripheral nerve sheath tumors (MPNST) represent a group of highly heterogeneous human malignancies often with multiple histological origins, divergent differentiation patterns, and diverse immunohistochemical presentations. The differential diagnosis of MPNST from other spindle cell neoplasms poses great challenges for pathologists. This report provides a mini-review of these unique features associated with MPNST and also presents the first cases of MPNST with six differentiation patterns.

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.

The loss of Nf1 transiently promotes self-renewal but not tumorigenesis by neural crest stem cells

Neurofibromatosis is caused by the loss of neurofibromin (Nf1), leading to peripheral nervous system (PNS) tumors, including neurofibromas and malignant peripheral nerve sheath tumors (MPNSTs). A long-standing question has been whether these tumors arise from neural crest stem cells (NCSCs) or differentiated glia. Germline or conditional Nf1 deficiency caused a transient increase in NCSC frequency and self-renewal in most regions of the fetal PNS. However, Nf1-deficient NCSCs did not persist postnatally in regions of the PNS that developed tumors and could not form tumors upon transplantation into adult nerves. Adult P0a-Cre+Nf1(fl/-) mice developed neurofibromas, and Nf1(+/-)Ink4a/Arf(-/-) and Nf1/p53(+/-) mice developed MPNSTs, but NCSCs did not persist postnatally in affected locations in these mice. Tumors appeared to arise from differentiated glia, not NCSCs.

A case of fibroblastic low-grade malignant peripheral nerve sheath tumor--a true neurofibrosarcoma

The authors report a case of low-grade retroperitoneal malignant peripheral nerve sheath tumor (MPNST) showing Schwannian and fibroblastic differentiation in individual tumor cells. The tumor was detected in a 29-year-old male and posed diagnostic difficulty because of the unusual morphologic and immunophenotypic features. Morphologic examination of the H&E sections revealed a rather circumscribed, highly vascular, moderately cellular spindle cell tumor. The neoplastic cells were arranged in vague, short fascicles, distributed haphazardly amid hemangiopericytoma-like vascular channels, and showed occasional whorls. Myxoid stroma and keloid-like collagen bundles were frequently seen. There were satellite nodules outside the main tumor mass and low mitotic activity but no necrosis. The tumor cells stained strongly and diffusely for both S-100 protein and CD34. Electron microscopy revealed cells with processes and focal lamina, and prominent rough endoplasmic reticulum. Although the capacity of MPNST to exhibit divergent differentiation is well known, fibroblastic differentiation is generally poorly and inconsistently documented. The present case represents an unambiguous demonstration of the co-expression within individual tumor cells of Schwannian and fibroblastic differentiation in a low-grade MPNST. The literature on this subject is reviewed.

Nestin expression as a new marker in malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumor (MPNST) can be difficult to diagnose because it lacks specific immunohistochemical markers. S-100, which is a useful marker of MPNST, has limited diagnostic utility. Recent studies suggest that nestin, which is an intermediate filament protein, is expressed in neuroectodermal stem cells. The diagnostic utility of immunostains for nestin and three other neural markers (S-100, CD56 and protein gene product 9.5 (PGP 9.5)) were evaluated in 35 cases of MPNST and in other spindle cell tumors. All MPNST cases were strongly positive for nestin and had cytoplasmic staining. Stains for S-100, CD56, and PGP 9.5 were positive in fewer cases (17/35, 11/35, and 29/35 cases, respectively), and had less extensive staining. Nestin was negative in 10/10 leiomyomas, and weak nestin expression was seen in 10/10 schwannomas, 3/10 neurofibromas, 2/8 synovial sarcomas, 2/10 liposarcomas, 4/7 carcinosarcomas and 3/7 malignant fibrous histiocytomas. In contrast, strong nestin positivity was seen in 10/10 rhabdomyosarcomas, 15/19 leiomyosarcomas, and 9/9 desmoplastic melanomas. Nestin is more sensitive for MPNST than other neural markers and immunostains for nestin in combination with other markers could be useful in the diagnosis of MPNST.

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.

Malignant peripheral nerve sheath tumors with high and low Ras-GTP are permissive for oncolytic herpes simplex virus mutants

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNSTs) occur most frequently in patients with neurofibromatosis type 1 and are often fatal. Current therapy relies upon radical surgical resection, which often fails to completely remove the tumor. To address the need for novel treatment approaches for this disease, we sought to determine if human MPNST-derived cell lines are sensitive to oncolytic Herpes simplex virus (oHSV) infection. Activation of the Ras pathway and its inhibitory effects on protein kinase R (PKR) activation have been shown to dictate cellular permissivity to oHSV mutants. Because NF-1-associated MPNSTs possess inherent hyperactive Ras, we hypothesized these tumors would be ideal therapeutic targets for oHSVs.

PROCEDURE

Human MPNST-derived cell lines were examined for sensitivity to oHSV-mediated gene transduction, virus replication, cytotoxicity, and apoptosis. These parameters were correlated with PKR activation following oHSV infection and compared with normal human Schwann cells (NHSCs) without hyperactive Ras.

RESULTS

MPNST-derived cell lines were efficiently transduced, supported virus replication and were killed by the oncolytic HSV mutants, including sporadic MPNSTs without hyperactive Ras. In contrast to the highly sensitive MPNST cell lines, NHSCs did not support mutant virus replication.

CONCLUSIONS

MPNSTs are susceptible to lysis by oncolytic HSV mutants, regardless of Ras status. Tumor-selective virus replication in MPNST cells appears to be mediated by both cellular expression of ribonucleotide reductase and prevention of eIF2alpha phosphorylation. Virus-induced cytotoxicity of MPNST cell lines was caused by both direct lysis and apoptosis. Our data suggest the use of oncolytic HSV mutants may represent a novel treatment approach for patients with MPNSTs.

Large-scale molecular comparison of human schwann cells to malignant peripheral nerve sheath tumor cell lines and tissues

Malignant peripheral nerve sheath tumors (MPNST) are highly invasive soft tissue sarcomas that arise within the peripheral nerve and frequently metastasize. To identify molecular events contributing to malignant transformation in peripheral nerve, we compared eight cell lines derived from MPNSTs and seven normal human Schwann cell samples. We found that MPNST lines are heterogeneous in their in vitro growth rates and exhibit diverse alterations in expression of pRb, p53, p14(Arf), and p16(INK4a) proteins. All MPNST cell lines express the epidermal growth factor receptor and lack S100beta protein. Global gene expression profiling using Affymetrix oligonucleotide microarrays identified a 159-gene molecular signature distinguishing MPNST cell lines from normal Schwann cells, which was validated in Affymetrix microarray data generated from 45 primary MPNSTs. Expression of Schwann cell differentiation markers (SOX10, CNP, PMP22, and NGFR) was down-regulated in MPNSTs whereas neural crest stem cell markers, SOX9 and TWIST1, were overexpressed in MPNSTs. Previous studies have implicated TWIST1 in apoptosis inhibition, resistance to chemotherapy, and metastasis. Reducing TWIST1 expression in MPNST cells using small interfering RNA did not affect apoptosis or chemoresistance but inhibited cell chemotaxis. Our results highlight the use of gene expression profiling in identifying genes and molecular pathways that are potential biomarkers and/or therapeutic targets for treatment of MPNST and support the use of the MPNST cell lines as a primary analytic tool.

An imprinted locus epistatically influences Nstr1 and Nstr2 to control resistance to nerve sheath tumors in a neurofibromatosis type 1 mouse model

Cancer is a complex disease in which cells acquire many genetic and epigenetic alterations. We have examined how three types of alterations, mutations in tumor suppressor genes, changes in an imprinted locus, and polymorphic loci, interact to affect tumor susceptibility in a mouse model of neurofibromatosis type 1 (NF1). Mutations in tumor suppressor genes such as TP53 and in oncogenes such as KRAS have major effects on tumorigenesis due to the central roles of these genes in cell proliferation and cell survival. Imprinted genes expressed from only one parental chromosome affect tumorigenesis if their monoallelic expression is lost or duplicated. Because imprinted loci are within regions deleted or amplified in cancer, the parental origin of genomic rearrangements could affect tumorigenesis. Gene polymorphisms can vary tumor incidence by affecting rate-limiting steps in tumorigenesis within tumor cells or surrounding stroma. In our mouse model of NF1, the incidence of tumors mutant for the tumor suppressor genes Nf1 and Trp53 is strongly modified by a linked imprinted locus acting epistatically on two unlinked polymorphic loci, Nstr1 and Nstr2. This interaction of an imprinted locus and polymorphic susceptibility loci has profound implications for human mapping studies where the parental contribution of alleles is often unknown.

Epithelioid malignant peripheral nerve sheath tumor involving maxillary sinus

We present a case of epithelioid malignant peripheral nerve sheath tumor (MPNST) located in the maxillary sinus region in a young man. The clinical history was short, but at admission the neoplastic infiltration was so extensive that only diagnostic biopsy was performed. The patient received palliative treatment and died 6 months later. Histologically, the neoplasm had a predominant epithelioid component. Neoplastic tissue was vimentin, S-100, Cam 5.2 and neuron-specific enolase positive. P53 protein reaction was found in 6% of the cells and the proliferation index assessed with Ki-67 was 52%. An appropriate immunohistochemical panel was essential for the final diagnosis of this epithelioid malignant tumor, with the location rather unusual for MPNST.

Proximal-Type Epithelioid Sarcoma: Report of Two Cases in the Perineum

The authors report two cases of perineal proximal-type epithelioid sarcoma in middle-aged men, age 51 and 43 years old. Both tumors were located in the right side. In the first patient a 7.5-cm, well-encapsulated tumor was completely excised. The second patient was a referral case with incomplete excision, but the computed tomography scan and magnetic resonance imaging showed a 14-cm nonencapsulated tumor involving the soft tissues of the inner thigh and perineum, as well as metastasis in right inguinal and retroperitoneal lymph nodes. Both neoplasms had a predominant solid pattern alternating with occasional discohesive areas. Both were composed of large oval to polygonal cells with vesicular nuclei, conspicuous nucleoli, and amphophilic to eosinophilic cytoplasm. Rhabdoid phenotype was identified in the second case only. The first neoplasm displayed 15% necrosis, 7 mitoses per 10 high-power field, focal vascular invasion, and no extracapsular invasion. The other exhibited 60% necrosis, 12 mitoses per 10 high-power fields, extensive vascular invasion, no distinct capsule, and invasion of the surrounding fatty tissue. Both were positive for vimentin, cytokeratin, epithelial membrane antigen, and CD34. Muscle-specific actin was negative in the first case and focally positive in the second. CD56 was positive in the second case and negative in the first case. Desmin, CD45, CD30, factor VIII, CD31, S100, HMB45, calretinin, and synaptophysin were negative in both. Since proximal-type epithelioid sarcoma can be confused with a number of other soft tissue tumors with epithelioid and/or rhabdoid features, the authors emphasize the immunohistochemical differential diagnosis.

Epithelioid malignant peripheral nerve sheath tumor. Report of a case with inflammatory infiltration

The epithelioid malignant peripheral nerve sheath tumor (EMPNST) is a rare sarcoma originating from the supportive non-neuronal components of peripheral nerves. Our patient was a 75-year-old Japanese man who presented with complaints about pain and a mass in the left thigh. Characteristic histopathological features were large epithelioid-like cells closely resembling a malignant melanoma or another type of soft tissue tumor. Notable infiltration of neutrophils in the tumor was seen. Immunohistochemically, the tumor cells proved positive for S-100, NSE, GFAP, MBP, chromogranin A and synaptophysin, and negative for CEA, keratin, HMB-45, G-CSF, and GM-CSF. Tumor-related inflammatory infiltration may be caused by an autonomous production of some cytokines. However, these tumor cells were negative for G-CSF and GM-CSF so that the mechanism triggering inflammatory infiltration is unclear. Electron microscopy revealed the presence of an extracellular basal lamina, intermediate cell junctions, and numerous dense-cored granules in the cytoplasm. These findings suggested a schwannian derivation, consistent with the diagnosis of EMPNST. There have been reports on S-100 positivity and HMB-45 negativity of this tumor type, but to the best of our knowledge, this is the first description of an EMPNST positive for MBP, chromogranin A, and synaptophisin. Where unequivocal features are lacking, these markers might be useful for differential diagnosis.

Immunohistochemical evaluation of canine peripheral nerve sheath tumors and other soft tissue sarcomas

Seventeen cases of canine peripheral nerve sheath tumors (PNSTs), 11 malignant PNSTs (MPNSTs), and six benign PNSTs (BPNSTs) were examined. The prognosis in five of six dogs with BPNSTs was excellent, whereas all dogs with MPNSTs died within 2 years after the last surgical resection. One BPNST formed a recurrent mass with features of a MPNST. Histopathologically, the predominant tumor cell of MPNSTs was either spindle or round in shape with epithelioid characteristics. Other atypical cells had abundant granular cytoplasm or were multinucleated giant cells with periodic acid-Schiff-positive cytoplasmic globules. Furthermore, two MPNSTs contained cartilaginous and osseous metaplasia. On the contrary, most BPNSTs exhibited typical features of schwannoma or neurofibroma, whereas two BPNSTs had atypical morphology. One BPNST consisted of epithelioid cell proliferation with some tumor cells revealing nuclear atypia. Immunohistochemically, the expression of vimentin (100%), S-100 (73%), nerve growth factor receptor (NGFR, 64%), and myoglobin (64%) was commonly found in MPNSTs. The two BPNSTs with atypical histologic appearances were positive for vimentin, S-100, NGFR, and neuron-specific enolase, and one of these had moderate immunoreactivity for cytokeratin. Most BPNSTs were positive for glial fibrillary acidic protein, as well as S-100 and NGFR. Although most rhabdomyosarcomas (RMSs) and canine hemangiopericytomas (CHPs) also showed focal immunoreactivity for S-100, most RMSs were intensely positive for myoglobin and negative for NGFR. Most CHPs (80%) exhibited focal alpha-smooth muscle actin (alpha-SMA) expression, whereas all PNSTs were negative. These results indicate that immunohistochemistry for NGFR and alpha-SMA might be useful for differentiating canine PNSTs from RMSs or CHPs, respectively.

Neural crest stem cells undergo multilineage differentiation in developing peripheral nerves to generate endoneurial fibroblasts in addition to Schwann cells

Neural crest stem cells (NCSCs) persist in peripheral nerves throughout late gestation but their function is unknown. Current models of nerve development only consider the generation of Schwann cells from neural crest, but the presence of NCSCs raises the possibility of multilineage differentiation. We performed Cre-recombinase fate mapping to determine which nerve cells are neural crest derived. Endoneurial fibroblasts, in addition to myelinating and non-myelinating Schwann cells, were neural crest derived, whereas perineurial cells, pericytes and endothelial cells were not. This identified endoneurial fibroblasts as a novel neural crest derivative, and demonstrated that trunk neural crest does give rise to fibroblasts in vivo, consistent with previous studies of trunk NCSCs in culture. The multilineage differentiation of NCSCs into glial and non-glial derivatives in the developing nerve appears to be regulated by neuregulin, notch ligands, and bone morphogenic proteins, as these factors are expressed in the developing nerve, and cause nerve NCSCs to generate Schwann cells and fibroblasts, but not neurons, in culture. Nerve development is thus more complex than was previously thought, involving NCSC self-renewal, lineage commitment and multilineage differentiation.

Hypertrophic neuropathies and malignant peripheral nerve sheath tumors in transgenic mice overexpressing glial growth factor beta3 in myelinating Schwann cells

The neuregulin-1 (NRG-1) family of growth and differentiation factors exerts a variety of effects on Schwann cells and their precursors during nervous system development; however, NRG-1 effects on adult Schwann cells are poorly defined. Several lines of evidence suggest that NRG-1 actions on adult Schwann cells are distinct from those observed during development. To test this hypothesis, we generated transgenic mice overexpressing the NRG-1 isoform glial growth factor beta3 (GGFbeta3) in myelinating Schwann cells [protein zero (P0)GGFbeta3 mice]. P0-GGFbeta3 mice develop resting tremors, gait abnormalities, decreased hindlimb strength, and paralysis by approximately 7 months of age. Sciatic nerves from these animals show a hypertrophic neuropathy characterized by demyelination, remyelination, and "onion bulb" formation. Development of this hypertrophic neuropathy is preceded by Schwann cell hyperplasia that is prominent in 1-month-old mice and present but decreased in 2- and 4-month-old animals. P0-GGFbeta3 mice also develop peripheral ganglion-associated malignant peripheral nerve sheath tumors. Motor, sensory, and sympathetic ganglia from 1-, 2-, and 4-month-old P0-GGFbeta3 mice uniformly contain intraganglionic, likely preneoplastic, Schwann cell proliferations. Examination of bromodeoxyuridine incorporation and caspase-3 activation in sciatic nerves and trigeminal ganglia indicates that Schwann cell hyperplasia in P0-GGFbeta3 mice reflects increased proliferation rather than decreased apoptosis. These observations are consistent with the hypothesis that GGFbeta3 induces proliferation of adult Schwann cells and demyelination of peripheral nerve axons. Furthermore, overexpression of this NRG-1 isoform frequently induces neoplastic Schwann cell proliferation within PNS ganglia, suggesting that NRG-1 may contribute to human Schwann cell neoplasia.

Malignant peripheral nerve sheath tumor with divergent mesenchymal differentiations in a dog

A malignant peripheral nerve sheath tumor with divergent osteogenic, myxomatous, and myoblastic differentiations is described in a 10.5-year-old male Labrador Retriever dog. The tumor involved the sixth and seventh cervical spinal cord segments and nerves. The diagnosis was based on the results of histopathology, electron microscopy, and immunohistochemistry.

Expression of claudin-1, a recently described tight junction-associated protein, distinguishes soft tissue perineurioma from potential mimics

Perineuriomas are rare benign soft tissue tumors having an immunophenotype paralleling the normal perineurial cell [S-100 protein negative and epithelial membrane antigen (EMA) positive]. Because EMA expression in perineuriomas may be focal and/or faint, there is continued interest in the development of new markers of perineurial differentiation. Perineurial cells differ from almost all other mesenchymal cell types by virtue of their formation of tight junctions. In the course of evaluating a group of novel tight junction-associated proteins, we noted high levels of expression of claudin-1 by normal perineurial cells and have systematically extended these observations to perineuriomas. Twelve EMA-positive/S-100-negative perineuriomas were retrieved from our consultation archives and compared with 39 tumors in the differential diagnosis of perineurioma (seven dermatofibrosarcoma protuberans, eight low-grade fibromyxoid sarcomas, three desmoplastic fibroblastomas, seven fibromatoses, nine neurofibromas, and five schwannomas). All cases were immunostained for claudin-1 using standard avidin-biotin technique. Cases were scored as 3+ (>50% positive cells), 2+ (25-50% positive cells), and 1+ (5-24% positive cells). In all cases positive internal controls in the form of epithelium, normal perineurium, or endothelial cells were present. Positive staining for claudin-1 was visualized in a distinctly particulate pattern along the cell membrane. Cytoplasmic staining was infrequent and was not scored as positive. Claudin-1 expression was present in 11 of 12 (92%) perineuriomas studied (seven at 3+, three at 2+, and one at 1+). In all but two cases, the degree of claudin expression was equal to or greater than the corresponding EMA immunostain. Claudin-1 expression was not noted in any cases of dermatofibrosarcoma protuberans, low-grade fibromyxoid sarcoma, desmoplastic fibroblastoma, or fibromatosis. Six of nine cases of neurofibroma contained a significant number of claudin-1-positive cells that were thought to be perineurial in origin, based on the staining of long, delicate cytoplasmic processes. One of four schwannomas contained a subpopulation of perivascular, dendritic, claudin-1-positive cells of presumed perineurial lineage. This is the first study to document expression of claudin-1 in perineurial cells and suggests a role for claudin-1 immunohistochemistry in the diagnosis of perineuriomas. Although claudin-1 should not replace EMA in the diagnosis of perineurioma, we think that it may play a valuable adjunctive role in difficult cases. In particular, claudin-1 is often a more robust marker than EMA in a given perineurioma. Claudin-1 is not expressed within the lesional cells of the mesenchymal tumors that enter into the differential diagnosis of perineurioma.

Neural fibrolipoma of the superficial peroneal nerve in the ankle: a case report with immunohistochemical analysis

This report presents a case of neural fibrolipoma arising from the superficial peroneal nerve in the ankle. A 28-year-old woman was referred with a soft tissue mass in the anterior aspect of the right ankle, which had been gradually enlarging for the past 10 years. Magnetic resonance imaging showed a mass lesion, measuring approximately 8 x 3 x 2 cm, with high to partially low signal intensity on both T1- and T2-weighted images. A band of low signal intensity within the lesion, which is indicative of coexistence with the tumor and the superficial peroneal nerve, could be detected on both T1- and T2-weighted images. The patient underwent an excisional biopsy. The specimen microscopically consisted of nerve bundles and fibro-fatty proliferation with abundant collagen fibers. Immunoreactivity for CD34 antigen antibody was detected in fibrous spindle cells. This is the first report to present an immunohistochemical profile of neural fibrolipoma. Neural fibrolipoma should be considered as a differential diagnosis when a lipomatous lesion is encountered in the foot or ankle as well as in the upper extremities.