Comparison of various basement membrane components in benign and malignant peripheral nerve tumours

Development of 3D culture models of plexiform neurofibroma and initial application for phenotypic characterization and drug screening

Plexiform neurofibromas (PNs), which may be present at birth in up to half of children with type 1 neurofibromatosis (NF1), can cause serious loss of function, such as quadriparesis, and can undergo malignant transformation. Surgery is the first line treatment although the invasive nature of these tumors often prevents complete resection. Recent clinical trials have shown promising success for some drugs, notably selumetinib, an inhibitor of MAP kinase kinase (MEK). We have developed three-dimensional (3D) cell culture models of immortalized cells from NF1 PNs and of control Schwann cells (SCs) that we believe mimic more closely the in vivo condition than conventional two-dimensional (2D) cell culture. Our goal is to facilitate pre-clinical identification of potential targeted therapeutics for these tumors. Three drugs, selumetinib (a MEK inhibitor), picropodophyllin (an IGF-1R inhibitor) and LDN-193189 (a BMP2 inhibitor) were tested with dose-response design in both 2D and 3D cultures for their abilities to block net cell growth. Cell lines grown in 3D conditions showed varying degrees of resistance to the inhibitory actions of all three drugs. For example, control SCs became resistant to growth inhibition by selumetinib in 3D culture. LDN-193189 was the most effective drug in 3D cultures, with only slightly reduced potency compared to the 2D cultures. Characterization of these models also demonstrated increased proteolysis of collagen IV in the matrix by the PN driver cells as compared to wild-type SCs. The proteolytic capacity of the PN cells in the model may be a clinically significant property that can be used for testing the ability of drugs to inhibit their invasive phenotype.

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 tumor invasion requires aberrantly expressed EGF receptors and is variably enhanced by multiple EGF family ligands

Aberrant epidermal growth factor receptor (EGFR) expression promotes the pathogenesis of malignant peripheral nerve sheath tumors (MPNSTs), the most common malignancy associated with neurofibromatosis type 1, but the mechanisms by which EGFR expression promotes MPNST pathogenesis are poorly understood. We hypothesized that inappropriately expressed EGFRs promote MPNST invasion and found that these kinases are concentrated in MPNST invadopodia in vitro. Epidermal growth factor receptor knockdown inhibited the migration of unstimulated MPNST cells in vitro, and exogenous EGF further enhanced MPNST migration in a substrate-specific manner, promoting migration on laminin and, to a lesser extent, collagen. In this setting, EGF acts as a chemotactic factor. We also found that the 7 known EGFR ligands (EGF, betacellulin, epiregulin, heparin-binding EGF, transforming growth factor-α [TGF-α], amphiregulin, and epigen) variably enhanced MPNST migration in a concentration-dependent manner, with TGF-α being particularly potent. With the exception of epigen, these factors similarly promoted the migration of nonneoplastic Schwann cells. Although transcripts encoding all 7 EGFR ligands were detected in human MPNST cells and tumor tissues, only TGF-α was consistently overexpressed and was found to colocalize with EGFR in situ. These data indicate that constitutive EGFR activation, potentially driven by autocrine or paracrine TGF-α signaling, promotes the aggressive invasive behavior characteristic of MPNSTs.

Molecular and Immunohistochemical Distinction of Equine Sarcoid From Schwannoma

Ten equine skin tumors that had been classified as schwannomas on routine histological examination were analyzed by polymerase chain reaction for bovine papillomavirus DNA. All 10 were positive for bovine papillomavirus 1 or 2, and all 10 were immunohistochemically negative for S-100 protein and strongly positive for vimentin. Nine tumors were moderately positive for laminin and 8, for smooth muscle actin. Five tumors were variably and weakly positive for type IV collagen. The lack of S-100 protein expression made Schwann cells an unlikely cell of origin, as opposed to peripheral nerve sheath tumors, which typically express S-100 protein, at least in some neoplastic cells. The immunohistochemical reactivity is consistent with myofibroblastic origin of the neoplastic cells, although smooth muscle cell or pericyte origin cannot be ruled out. These tumors represent an atypical form of equine sarcoid. Polymerase chain reaction for bovine papillomavirus and S-100 immunohistochemistry are strongly recommended for all equine skin tumors with histological characteristics typical of schwannoma or peripheral nerve sheath tumor.

Neuregulin-1 beta and neuregulin-1 alpha differentially affect the migration and invasion of malignant peripheral nerve sheath tumor cells

Malignant peripheral nerve sheath tumors (MPNSTs) are the most common malignancy associated with neurofibromatosis Type 1 (NF1). These Schwann cell lineage-derived sarcomas aggressively invade adjacent nerve and soft tissue, frequently precluding surgical resection. Little is known regarding the mechanisms underlying this invasive behavior. We have shown that MPNSTs express neuregulin-1 (NRG-1) beta isoforms, which promote Schwann cell migration during development, and NRG-1 alpha isoforms, whose effects on Schwann cells are poorly understood. Hypothesizing that NRG-1 beta and/or NRG-1 alpha promote MPNST invasion, we found that NRG-1 beta promoted MPNST migration in a substrate-specific manner, markedly enhancing migration on laminin but not on collagen type I or fibronectin. The NRG-1 receptors erbB3 and erbB4 were present in MPNST invadopodia (processes mediating invasion), partially colocalized with focal adhesion kinase and the laminin receptor beta(1)-integrin and coimmunoprecipitated with beta(1)-integrin. NRG-1 beta stimulated human and murine MPNST cell migration and invasion in a concentration-dependent manner in three-dimensional migration assays, acting as a chemotactic factor. Both baseline and NRG-1 beta-induced migration were erbB-dependent and required the action of MEK 1/2, SAPK/JNK, PI-3 kinase, Src family kinases and ROCK-I/II. In contrast, NRG-1 alpha had no effect on the migration and invasion of some MPNST lines and inhibited the migration of others. While NRG-1 beta potently and persistently activated Erk 1/2, SAPK/JNK, Akt and Src family kinases, NRG-1 alpha did not activate Akt and activated these other kinases with kinetics distinct from those evident in NRG-1 beta-stimulated cells. These findings suggest that NRG-1 beta enhances MPNST migration and that NRG-1 beta and NRG-1 alpha differentially modulate this process.

Immunohistochemical characterization of capsular cells in neuromuscular spindles of the neck

BACKGROUND

To identify capsular components of neuromuscular spindles in man by means of immunohistochemistry.

METHODS

Investigation of histologically observed neuromuscular spindles in surgical specimens with the use of markers for sheath cells and basement membranes.

RESULTS

Epithelial membrane antigen and CD34 immunoreactivities were found in the outer and inner capsular layers, respectively. S-100 protein was not expressed in the capsules and there was more collagen type IV than laminin.

CONCLUSIONS

Cells resembling perineurial cells and endoneurial fibroblasts, and basement membrane rich in collagen type IV comprise the capsules of neuromuscular spindles.

Multiple schwannomas: report of two cases

In this paper authors present two cases of multiple schwannomas without the features of neurofibromatosis (NF). The authors retrospectively reviewed the hospital charts, radiology films, operative notes and pathology slides of these two patients. There was no family history of neurofibromatosis. The two patients had contrast enhanced MRI, which was negative for vestibular schwannomas. Both underwent surgical excision of symptomatic lesions. Histopathology confirmed these lesions as schwannomas. Molecular genetic analysis in case 1 demonstrated two distinct mutations of the NF2 gene in two different schwannomas, with concomitant loss of heterozygosity in both tumours. In contrast peripheral blood lymphocytes did not reveal mutations of NF2. The authors recommend surgery for symptomatic lesions. Asymptomatic tumours can be monitored. Regular follow up is essential as they may develop fresh lesions at any time. The relevant literature is discussed.

Diagnosis and treatment options for nerve sheath tumors

The purpose of this review is to discuss the contemporary diagnosis and treatment options for nerve sheath tumors. Common nerve sheath tumors include schwannomas, neurofibromas and malignant nerve sheath tumors. Nerve sheath tumors can be associated with genetic disorders such as neurofibromatosis and schwannomatosis. There is great variation in terms of tumor location, clinical presentation and treatment strategy. Magnetic resonance imaging is the diagnostic study of choice for nerve sheath tumors and surgery has become the mainstay of treatment for most symptomatic lesions. Progress in microsurgical techniques has resulted in significant improvement in surgical outcome, with preservation of neurologic function. Complete resection of benign nerve sheath tumors is the goal of surgical intervention and this results in cure. In contrast, malignant nerve sheath tumors remain a major challenge with poor outcomes overall. Progress in multidisciplinary research may ultimately lead to novel therapeutic strategies.

Structural organization of subgemmal neurogenous plaques in foliate papillae of tongue

Little is known about subgemmal neurogenous plaques in the foliate papillae of tongue, which prompted the present investigation. The plaques were immunohistochemically studied in biopsies from 16 adults with the use of neural, stromal, basement membrane, and cell-cycle markers. They displayed a zonal pattern of organization. The neurofibroma-like superficial zone expanded lamina propria and was contiguous to the epithelium covering the papillae. It consisted of tangled composites of S-100 protein-positive spindled cells and fibrils stained for protein gene product 9.5 and neurofilament protein. The composites also expressed the CD56 antigen, could be traced into overlying taste buds, were associated with abundant laminin, and were intermingled with scattered dendritic cells expressing factor XIIIalpha and with mast cells decorated on staining for CD117. Similar composites, but arranged in fascicles and invested by epithelial membrane antigen-positive and collagen IV-positive sheaths, characterized the deep zone of the plaques. Intrafascicular CD57-positive myelin-like annuli and CD34-positive spindled cells were also features of this zone. The sheaths and, most often, the CD57-positive annuli and CD34-positive cells were progressively spread apart toward the intermediate zone of the plaques and were lost superficially. Ki67 and Bcl-1 were not expressed in the plaques. The results suggest that composites of Schwann cells and unmyelinated axons make up the superficial bulk of the plaques, whereas perineurial cells, endoneurial fibroblasts, and myelinated axons are present more deeply. It is possible that the composites achieve neuroeffector relationships and are not neoplastic. Trophic influences from gustatory nerve fibers could play a role in the development of the plaques.

Immunohistochemical and Ultrastructural Comparative Study of External Lamina Structure in 31 Cases of Cellular, Classical, and Melanotic Schwannomas

Unlike most soft tissue tumors, schwannoma is characterized by the presence of distinct linear, frequently duplicated external lamina (EL). Although electron microscopy remains the gold standard for demonstrating this unique feature and distinguishing its morphologic variants from mimickers, the use of two anti-EL antibodies, laminin and type IV collagen, appears to supersede electron microscopy in terms of current practice. To determine whether immunohistochemical expression correlates with ultrastructural findings, 10 cellular schwannomas, 18 classic schwannomas, and 3 melanotic schwannomas were evaluated ultrastructurally and immunohistochemically using antibodies to type IV collagen and laminin. Immunohistochemically, a moderate to strong intensity in more than 50% of tumor cells was detected using either antibody in most cases of cellular schwannomas (70%), the Antoni A areas of classic schwannomas (78%), and melanotic schwannomas (67%). Ultrastructurally, the presence of diffusely continuous, duplicated EL was observed in 30% of cellular schwannomas and 56% of classic schwannomas, while 50% of cellular schwannomas and 22% of classic schwannomas showed either continuous simple EL or discontinuous but duplicated EL alone. In addition, two cellular schwannomas (20%) and four classic schwannomas (22.2%) had only a simple layer of EL in focal areas. In contrast to the distinct immunostaining surrounding individual cells seen in the former two subtypes, all three melanotic schwannomas displayed a biphasic-staining pattern of the EL (ie, individual cell and nested), which was confirmed at the ultrastructural level. The authors found a significant difference in intensity between the Antoni A and B areas of classic schwannomas using both laminin and type IV collagen. In addition, the intensities of laminin and type IV collagen in the Antoni A areas of classic schwannomas were significantly stronger compared with those of cellular schwannomas. Nevertheless, there was no significant difference either between two antibodies or between cellular and classic variants with regard to the extent of immunoreaction. Only in classic schwannomas did the extent of immunoreaction against both laminin and type IV collagen correlate significantly with the ultrastructural EL distribution pattern (diffusely continuous vs. discontinuous). However, this association was not detected in cases of cellular schwannomas. On the other hand, the intensities of laminin and type IV collagen did not correlate with the ultrastructural thickness of EL, irrespective of the morphologic subtypes. In conclusion, both type collagen IV and laminin are still reliable markers of EL in various types of schwannomas. Schwannomas exhibiting a monolayered EL are as strong in immunoreaction as those displaying reduplicated/thickened EL, indicating that a single layer of EL is thick enough to be identified by both antibodies with sufficient sensitivity. The peculiar biphasic EL pattern seen in melanotic schwannoma remains under-recognized, which may lead to misdiagnosis as malignant melanomas, especially in limited biopsy specimens.

Inflammatory pseudotumor of the median nerve. Case report and review of the literature

The authors report the presence of an inflammatory pseudotumor of the median nerve in a young woman who presented with a sensorimotor deficit in the median nerve area. Magnetic resonance (MR) images revealed a fusiform mass in the nerve, and the patient underwent surgery for a suspected peripheral nerve-sheath tumor. Her clinical condition improved slowly and notably. Histological study revealed a heterogeneous lymphoid infiltration with mononuclear cells, lymphocytes (mostly T cells), and plasmocytoid cells. Because of the unknown significance of this infiltration, the patient was examined to exclude the possible diagnosis of a systemic tumoral process. All the studies yielded negative results and no systemic disease was found. Later, control MR imaging revealed no tumoral remains, and electromyography demonstrated progressive improvement of median nerve function. The follow-up period has been 8 years. The cause of the lesion is unknown. The differential diagnosis includes benign and malignant peripheral nerve-sheath tumors, lymphoma, and all tumorlike lesions of peripheral nerves.

Intraosseous epithelioid malignant peripheral nerve sheath tumor of the phalanx. Case report

We report the first case of intraosseous epithelioid malignant peripheral nerve sheath tumor (MPNST) occurring in the phalanx. The patient was a 50-year-old Japanese man with an intramedullary lytic lesion of the proximal phalanx. Microscopically, the tumor was composed of epithelioid cells or polygonal cells, forming large cell nests with central necrosis. Most tumor cells were diffusely and strongly immunopositive for S-100 protein and vimentin, and negative for cytokeratin, epithelial membrane antigen, carcinoembryonic antigen, alpha-smooth muscle actin, and HMB-45. Laminin-positive material was discontinuously demonstrated between the individual tumor cells. Electron microscopy showed prominent external lamina. Our case indicated that laminin is useful for differentiating epithelioid MPNST from metastatic carcinoma and malignant melanoma.

Poorly differentiated synovial sarcoma: immunohistochemical distinction from primitive neuroectodermal tumors and high-grade malignant peripheral nerve sheath tumors

Synovial sarcoma is a relatively common sarcoma in adults, which in its classic bimorphic form infrequently poses a diagnostic problem. Monomorphic spindled variants, as well as the less common poorly differentiated variants, may be confused with other soft-tissue sarcomas; the poorly differentiated variant (PDSS), in particular, may be histologically indistinguishable from other small, blue, round cell tumors, including primitive neuroectodermal tumors (PNETs). Detection of the synovial sarcoma-associated t(X;18) by either cytogenetic or molecular genetic approaches may be necessary to confirm the diagnosis of synovial sarcoma in difficult cases. We evaluated 10 cases of PDSS from eight patients using a panel of antibodies (including those to intermediate filament proteins, nerve-sheath associated markers, and neuronal and neuroectodermal associated markers) in order to better establish the immunophenotype of this tumor and to help distinguish it from the tumors with which it may be confused, particularly PNETs and high-grade malignant peripheral nerve sheath tumors (MPNSTs). Our results showed PDSS to have significant immunophenotypic overlap with both PNETs and MPNSTs. In most instances these three entities may be differentiated by a panel of antibodies that should include those to both low and high molecular weight cytokeratins, epithelial membrane antigen, type IV collagen, CD99, CD56, and S-100 protein. Our results also suggest that synovial sarcoma may be a tumor showing combined neuroectodermal and nerve sheath differentiation--perhaps because of translocation-associated expression of specific proteins--rather than a carcinosarcoma of soft tissues or a tumor of specialized arthrogenous mesenchyme.

Nerve sheath tumours with hybrid features of neurofibroma and schwannoma: a conceptual challenge

AIMS

To characterize and delineate a subset of rare nerve sheath tumours showing hybrid features of neurofibroma and schwannoma.

METHODS AND RESULTS

Nine lesions were identified in the authors' files showing predominant features of neurofibroma with distinct, often nodular regions of classical schwannomatous differentiation. Most patients were adults, eight out of nine were male. Of the nine lesions, two were dermal, two were subcutaneous and five were subfascial. Five lesions had a plexiform architecture and one patient had overt neurofibromatosis. One out of six patients with follow-up developed local recurrence. Schwannoma-like regions displayed strong S100 staining, in contrast to more varied and limited S100 reactivity in neurofibromatous areas. The Antoni A areas could be quite cellular with high MIB-1 proliferation indices. No lesion underwent malignant change.

CONCLUSIONS

Our results demonstrate that some nerve sheath tumours may contain histologically clear components of both neurofibroma and schwannoma, suggesting that (despite evident and well-defined clinicopathological differences) these two lesions may be even more closely related than previously recognized. Whether this phenomenon results from a localized microenvironmental change or from a clonal genetic alteration remains unknown.

Benign neural tumors of the oral cavity: a comparative immunohistochemical study

To determine if immunohistochemistry can be used as adjunct to the diagnosis and classification of oral benign neural tumors, we stained 77 neurally differentiated tumors with a panel of neural-associated antibodies (S-100 protein, CD57, epithelial membrane antigen, factor XIIIa, CD34, CD68, collagen IV). Using standard histologic criteria, we identified 13 schwannomas, 16 neurofibromas, 23 traumatic neuromas, 16 palisaded and encapsulated neuromas, and 9 granular cell tumors from archived oral pathology specimens. Silver stains showed that neurofibromas, traumatic neuromas, and palisaded and encapsulated neuromas consistently contained axon filaments. Although all neural tumors contained S-100-positive cells, schwannomas and palisaded and encapsulated neuromas contained the most. All tumors expressed CD57; traumatic neuromas were stained intensely and the others stained weakly. The consistent epithelial membrane antigen capsular staining of schwannomas and the absence of factor XIIIa-positive dendritic/spindle cells helped distinguish these tumors from others. Many CD34-positive cells were found in schwannomas, and few were found in palisaded and encapsulated neuromas. Variable numbers CD68-positive cells were seen in all neural tumor types; some of these cells appeared to be macrophages and mast cells, but many were thought to be Schwann cells expressing this antigen. Collagen IV staining, apparently representing basement membrane, was generally a feature of all benign neural tumors. The immunophenotype of the granular cells of the GCTs was S-100+, CD57+, and collagen IV+ supporting the putative neural origin of these tumors. We conclude that neural origin/differentiation of a connective tissue tumor can be confirmed with stains for S-100 protein, epithelial membrane antigen, CD57, and collagen IV. Staining patterns and intensities associated with the panel of antibodies tested can be useful in tumor classification.

Major basement membrane components in Kaposi's sarcoma, angiosarcoma and benign vascular neogenesis

Recent cell biologic studies have emphasized the importance of the basement membrane (BM) and its molecular components in angiogenesis. We immunostained 60 angioproliferative lesions (angiosarcoma, sclerosing hemangioma of skin, pyogenic granuloma, capillary hemangioma, lymphangioma, glomangioma and granulation tissue) and 23 cases of Kaposi's sarcoma (KS) for the major macromolecular components laminin, collagen type IV, fibronectin and heparan sulfate proteoglycan (HSPG). Normal structures served as aggregate controls in each group, and semiquantitative scoring reflected the degree of consistency of staining about blood and lymphatic endothelium and vascular sheath (pericyte/smooth muscle) within and peripheral to each lesion. Benign and reactive vasoproliferations consistently maintained immunoreactivity for each BM component around endothelium and sheath components of blood vessels. Angiosarcoma showed from 20 to more than 60% less consistent immunoreactivity by comparison, although the score variances were greater than for non-malignant lesions. Staining about blood vessel endothelium was both strong and consistent among histologic stages in KS with the exception of HSPG, which was weakly immunoreactive in all stages. Marked selective HSPG loss was characteristic only of KS and normal lymphendothelium, and in the light of evidence for a role for HSPG in the assembly and maintenance of BM, suggests that reduced HSPG may be responsible for the loss of ultrastructural integrity of perivascular BM in both.