Epithelial membrane antigen expression by the perineurium of peripheral nerve and in peripheral nerve tumours

Specimens of normal peripheral nerve and a series of peripheral nerve lesions have been immunostained with three different anti-epithelial membrane antigen (EMA) monoclonal antibodies. Sites of EMA immunoreactivity have been confirmed within perineurial cells of peripheral nerve, noted within the capsule of Schwannomas and palisaded encapsulated neuromas, and also detected with traumatic neuromas and plexiform neurofibromas. No expression was detected within simple neurofibromas, diffuse neurofibromas or within malignant Schwannomas. These sites of EMA expression concur with the suggested involvement of perineurial cells in the formation of the particular lesions. The relationship between EMA expression by the perineurium and the piaarachnoid membrane is discussed.     

Microscopic intraneural perineurial cell proliferations in patients with neurofibromatosis type 1

Benign peripheral nerve sheath tumors (PNSTs) showing more than one line of differentiation (hybrid PNSTs) have been increasingly recognized, mainly due to awareness of their existence and as a consequence of increased use of immunohistochemisty during the last decade. Two recent studies suggested overrepresentation of hybrid tumors among benign PNSTs in patients with neurofibromatosis type 1 (NF-1). This study was performed to assess the presence of perineurial cells in microscopic (early) neurofibromatous lesions and normal-looking peripheral nerves in specimens from 5 patients with NF-1 using markers of perineurial cell differentiation (epithelial membrane antigen, claudin-1, and glucose transporter 1). In 2 patients, multiple normal looking nerve fibers as well as hypertrophied nerves and microscopic tumor nodules showed variable intraneural perineurial cell proliferations that frequently occupied the whole nerve fascicle resulting in multiple microscopic reticular perineurioma-like nodules (microscopic hybrid neurofibromatosis/perineuriomatosis). None of the cases showed the onion skin pattern of intraneural perineurioma. However, other nerve fibers within the same specimens showed normal compact rim of perineurium without any detectable intraneural perineurial cells. Both patients had concurrent multiple larger PNSTs (plexiform neurofibromas, hybrid neurofibroma/perineurioma and lesions with features intermediate between the 2 types). One specimen harboring high-grade malignant PNST and 2 specimens with large solitary neurofibromas displayed no intraneural perineurial cells. These observations suggest that intraneural perineurial proliferations are part of the early lesions in the setting of constitutional NF-1 inactivation and support the concept of pure and hybrid perineuriomatous lesions as novel member of the spectrum of PNSTs in NF-1.     

The enigmatic perineurial cell and its participation in tumors and in tumorlike entities.

The perineurial cells that make up the perineurium of peripheral nerve fascicles are characterized by distinct ultrastructural features, including non-branching thin cytoplasmic processes coated by an external lamina and joined at their ends by a tight junction, few organelles, actin and vimentin filaments, and numerous pinocytotic vesicles. Perineurial cells are immunoreactive for vimentin and epithelial membrane antigen (EMA) but not for the Schwann cell markers S-100 protein and Leu-7. The cytogenesis of the perineurium remains disputable, with morphologic, immunohistochemical, and experimental evidence supporting origin from the fibroblast, Schwann cell, and arachnoid cap cell. Ultrastructural studies more recently supported by immunolocalization of EMA have detected hyperplastic and neoplastic perineuriallike cells in a number of pseudoneoplastic lesions and true neoplasms, notably localized hypertrophic neuropathy, neurofibromas of various types, and perineurioma.     

The Enigmatic Perineurial Cell and Its Participation in Tumors and in Tumorlike Entities

The perineurial cells that make up the perineurium of peripheral nerve fascicles are characterized by distinct ultrastructural features, including non-branching thin cytoplasmic processes coated by an external lamina and joined at their ends by a tight junction, few organelles, actin and vimentin filaments, and numerous pinocytotic vesicles. Perineurial cells are immunoreactive for vimentin and epithelial membrane antigen (EMA) but not for the Schwann cell markers S-100 protein and Leu-7. The cytogenesis of the perineurium remains disputable, with morphologic, immunohistochemical, and experimental evidence supporting origin from the fibroblast, Schwann cell, and arachnoid cap cell. Ultrastructural studies more recently supported by immunolocalization of EMA have detected hyperplastic and neoplastic perineuriallike cells in a number of pseudoneoplastic lesions and true neoplasms, notably localized hypertrophic neuropathy, neurofibromas of various types, and perineurioma.     

The Enigmatic Perineurial Cell and Its Participation in Tumors and in Tumorlike Entities

The perineurial cells that make up the perineurium of peripheral nerve fascicles are characterized by distinct ultrastructural features, including non-branching thin cytoplasmic processes coated by an external lamina and joined at their ends by a tight junction, few organelles, actin and vimentin filaments, and numerous pinocytotic vesicles. Perineurial cells are immunoreactive for vimentin and epithelial membrane antigen (EMA) but not for the Schwann cell markers S-100 protein and Leu-7. The cytogenesis of the perineurium remains disputable, with morphologic, immunohistochemical, and experimental evidence supporting origin from the fibroblast, Schwann cell, and arachnoid cap cell. Ultrastructural studies more recently supported by immunolocalization of EMA have detected hyperplastic and neoplastic perineuriallike cells in a number of pseudoneoplastic lesions and true neoplasms, notably localized hypertrophic neuropathy, neurofibromas of various types, and perineurioma.     

Ultrastructural Study of a Perineurioma with Ribosome-Lamella Complexes

The participation of the perineurial cell in peripheral nerve tumors is the subject of much debate. The case of a 75-year-old female with a soft tissue tumor on her left shoulder is presented. The tumor had histological, ultrastructural, and immunohistochemical characteristics of a pure perineurial cell neoplasm. Ultrastructurally, distinctive ribosome-lamella complexes were found in the cytoplasm of the perineurial cells. This may be the first time that these structures have been described in perineurioma.     

Malignant peripheral nerve sheath tumors: an immunohistochemical study in relation to ultrastructural features.

The constituent cells in malignant peripheral nerve sheath tumors were examined by studying the expression of immunohistochemical markers for Schwann cells and perineurial cells in relation to ultrastructural features in 12 malignant peripheral nerve sheath tumors. Ultrastructural studies demonstrated mixed proliferation of Schwann cells, perineurial cells, fibroblastic cells, and primitive cells in many malignant peripheral nerve sheath tumors. Expression of S-100 protein was well correlated with Schwann cell-like differentiation of tumor cells. However, Leu-7 and epithelial membrane antigen, which have been considered to be specific to Schwann cells and perineurial cells, respectively, were common to Schwann cells, perineurial cells, and primitive cells. The common immunophenotypic expression suggests a close relationship among these cell types. The unusual expression of cytokeratin could be explained by the plasticity of intermediate filament expression.     

Ultrastructural Study of a Perineurioma

A case of soft tissue tumor in the left brachialis muscle of a 49-year-old Japanese female patient was studied by electron microscopy. The tumor was diagnosed as intramuscular myxoma by light microscopy, but electron microscopic observation revealed that the tumor almost entirely consisted of cells similar to normal perineurial cells. The tumor cells possessed long, slender cytoplasmic processes covered by well-developed but discontinuous basal laminae, clusters of pinocytotic vesicles, and infrequent intercellular junctions. Perineurial cells have also been observed in other peripheral nerve lesions: neurofibromas, nerve sheath myxomas, and localized hypertrophic neuropathies. However, the term “perineurioma” or “perineurial cell tumor” should be reserved for discrete tumorous masses that are almost entirely composed of perineurial cells without evidence of residual axons, Schwann cells, fibroblasts, or tactile corpusclelike structures. Perineurioma may represent a third category of peripheral nerve sheath tumors, ultrastruc-turally distinct from schwannomas and neurofibromas.     

Ultrastructural Study of a Perineurioma

A case of soft tissue tumor in the left brachialis muscle of a 49-year-old Japanese female patient was studied by electron microscopy. The tumor was diagnosed as intramuscular myxoma by light microscopy, but electron microscopic observation revealed that the tumor almost entirely consisted of cells similar to normal perineurial cells. The tumor cells possessed long, slender cytoplasmic processes covered by well-developed but discontinuous basal laminae, clusters of pinocytotic vesicles, and infrequent intercellular junctions. Perineurial cells have also been observed in other peripheral nerve lesions: neurofibromas, nerve sheath myxomas, and localized hypertrophic neuropathies. However, the term “perineurioma” or “perineurial cell tumor” should be reserved for discrete tumorous masses that are almost entirely composed of perineurial cells without evidence of residual axons, Schwann cells, fibroblasts, or tactile corpusclelike structures. Perineurioma may represent a third category of peripheral nerve sheath tumors, ultrastruc-turally distinct from schwannomas and neurofibromas.     

Relationship between fascicle size and perineurial collagen IV content in diabetic and control human peripheral nerve

Aim: The relationship between perineurial collagen IV content and fascicle size was determined in diabetic and control human peripheral nerve. METHODS AND RESULTS: Age-matched diabetic and control sural nerve samples were immunostained using antibodies to collagen IV. The number of cell layers and the perimeter of the fascicle were measured and the collagen IV content of the perineurium determined. Using this method, a comparison could be made of collagen IV content in the perineuria of fascicles of different size. A positive linear relationship was found between fascicle size and the amount of collagen IV per unit of perineurium. The number of perineurial cell layers and the collagen IV content of the diabetic nerve did not differ from control values. CONCLUSIONS: The linear relationship between fascicle size and perineurial collagen IV content per unit of perineurium underlines the importance of taking fascicle size into account when determining changes in basement membrane components associated with neuropathy. The results indicate that increased deposition of collagen IV is not involved in the early changes in the perineurial cell basement membrane and is thus not the primary factor involved in altered nerve function associated with diabetic neuropathy.     

Neural architecture in transected rabbit sciatic nerve after prolonged nonreinnervation

Observations have been made on the rabbit sciatic nerve distal to a transection, with survival periods of up to 26 mo and prevention of reinnervation. It was confirmed that the nerve becomes compartmented by fibroblast processes and that a zone of fine collagen fibrils develops around the Schwann cell columns that constitute the Büngner bands. The Schwann cells become progressively more atrophic but after 6 mo of denervation still expressed low affinity p75 nerve growth factor receptor (NGFR), the latest stage at which this was examined. NGFR was also expressed by the processes of the fibroblasts producing the endoneurial compartmentation. By 26 mo after transection the site of previous nerve fibres was indicated by sharply demarcated domains of approximately circular outline in transverse section consisting of densely packed longitudinally oriented collagen fibrils. Some of these domains still possessed centrally situated Schwann cells or residual basal lamina but many were acellular. The central collagen fibrils in these domains were of smaller diameter than those situated peripherally but were of larger size than those that form around the Büngner bands during wallerian degeneration. The peripherally located fibrils in the domains were of the same calibre as for normal endoneurial collagen. The collagen domains were encircled by fibroblast processes or at times enclosed in a perineurial cell ensheathment. Long-standing axonal loss therefore leads to a striking reorganisation of the internal architecture of peripheral nerve trunks. The findings may be relevant for the interpretation of the appearances in chronic peripheral neuropathies in man.     

Immunohistochemical demonstration of EMA/Glut1-positive perineurial cells and CD34-positive fibroblastic cells in peripheral nerve sheath tumors.

To clarify the cellular composition of various peripheral nerve tumorous lesions (traumatic neuroma, 5 cases; schwannoma, 10 cases; neurofibroma, 14 cases; perineurioma, 3 cases; conventional malignant peripheral nerve sheath tumor (MPNST), 7 cases; perineurial MPNST, 4 cases), expression of several markers specific to nerve sheath cells, including glucose transporter protein 1 (Glut1) and CD34, were immunohistochemically investigated with highly sensitive detection methods. In normal nerves and neuromas, perineuriums were positive for Glut1 as well as for epithelial membrane antigen (EMA), and there were some CD34-positive fibroblast-like cells in the endoneurium. Schwannomas consisted principally of S-100 protein-positive Schwann cells, whereas a few CD34-positive fibroblastic cells were present in Antoni B areas. Neurofibromas and conventional MPNST exhibited a mixed proliferation of S-100 protein-, EMA/Glut1-, and CD34-positive cells, indicating a heterogeneous composition of the constituents. The catalyzed signal amplification (CSA) system demonstrated more numerous EMA-positive perineurial cells in neurofibromas than did the ENVISION+ method. Perineurial cell tumors (benign and malignant) were composed of EMA/Glut1-positive and S-100 protein-negative tumor cells. The present study confirmed the characteristic cellular composition to each nerve sheath tumor immunohistochemically and showed the usefulness of the nerve sheath cell markers. Glut1 as well as EMA are specific to perineurial cells, and CD34 seems to be immunoreactive to endoneurial fibroblasts.     

Perineurial cell tumor

Summary A perineurial cell tumor occurred in the shoulder girdle of a 47 year old woman. Light microscopy demonstrated a well-differentiated spindle-cell neoplasm of uncertain histogenesis. Immunocytochemical staining for S-100 protein was negative. Ultrastructural study revealed tumor cells with characteristics of perineurium, e.g. large numbers of micropinocytotic vesicles, numerous intercellular junctions, and elongated cell processes surrounded by basal lamina. Tumors of perineurial cells should be distinguished from the commonly recognized schwannomas as well as from various soft tissue lesions so that their biologic behavior can be better defined. A review of three other reported cases of perineurial cell tumors suggested that these tumors are benign and are usually located in the extremities and shoulder girdle. In addition, perineurial cell proliferation has been identified in other lesions of peripheral nerves, such as neurofibromas and localized hypertrophic neuropathy. Immunocytochemical and ultrastructural study of spindle-cell lesions with unusual histologic features may reveal that perineurial cell proliferation occurs more frequently than currently recognized.     

Mammalian Nkx2.2+ perineurial glia are essential for motor nerve development

Results: In conjunction with RNA expression analysis and antibody labeling, we observed Nkx2.2⁺ cells along peripheral motor nerves at all stages of development and in adult tissue. Additionally, in mice lacking Nkx2.2, we demonstrate that Nkx2.2⁺ perineurial glia are essential for motor nerve development and Schwann cell differentiation. 相似文献   

Actin bundles in perineurial cells of rat spinal nerves

The overall distribution of the actin cytoskeleton in perineurial cells of rat spinal nerves was examined by confocal laser and thin-section electron microscopy. Confocal laser microscopy of whole-mount nerves stained with fluorescent-labelled phalloidin revealed two types of actin bundles in perineurial cells; stress fiber-type actin bundles and circumferential actin bundles. The degree of development of the actin cytoskeleton varied in different segments of different nerves. Stress fiber-type actin bundles were also immunostained for myosin and vinculin and were well-developed in the perineurial cells of large-sized nerves and dorsal root ganglia, whereas they were poor in spinal nerve root sheaths within the subarachnoid space. In peripheral nerves, stress fiber-type actin bundles tended to be arranged transverse to the nerve axis. Circumferential actin bundles were localized along intercellular junctions, which were immunostained with several junctional proteins such as –catenin, occludin and ZO-1. Thin-section electron microscopy confirmed the distribution pattern of actin bundles observed by confocal laser microscopy. These findings suggest that actin bundles may play some roles in structurally stabilizing the perineurium by providing mechanical support for the cell layers as well as cell junctions to maintain perineurial integrity and form diffusion barriers in peripheral nerves.     

Synovial sarcoma of nerve

Tumors of peripheral nerve are largely neuroectodermal in nature and derived from 2 elements of nerve, Schwann or perineurial cells. In contrast, mesenchymal tumors affecting peripheral nerve are rare and are derived mainly from epineurial connective tissue. The spectrum of the latter is broad and includes lipoma, vascular neoplasms, hematopoietic tumors, and even meningioma. Of malignant peripheral nerve neoplasms, the vast majority are primary peripheral nerve sheath tumors. Malignancies of mesenchymal type are much less common. To date, only 12 cases of synovial sarcoma of nerve have been described. Whereas in the past, parallels were drawn between synovial sarcoma and malignant glandular schwannoma, an uncommon form of malignant peripheral nerve sheath tumor, molecular genetics have since clarified the distinction. Herein, we report 10 additional examples of molecularly confirmed synovial sarcoma, all arising within minor or major nerves. Affecting 7 female and 3 male patients, 4 tumors occurred in pediatric patients. Clinically and radiologically, most lesions were initially thought to be benign nerve sheath tumors. On reinterpretation of imaging, they were considered indeterminate in nature with some features suspicious for malignancy. Synovial sarcoma of nerve, albeit rare, seems to behave in a manner similar to its more common, soft tissue counterpart. Those affecting nerve have a variable prognosis. Definitive recommendations regarding surgery and adjuvant therapies await additional reports and long-term follow-up. The literature is reviewed and a meta-analysis is performed with respect to clinicopathologic features versus outcome.     

Microfasciculation: a morphological pattern in leprosy nerve damage

Antunes S L G, Medeiros M F, Corte‐Real S, Jardim M R, da Costa Nery J A, Hacker M A V B, da Costa Valentim V, Amadeu T P & Sarno E N
(2011) Histopathology 58, 304–311 Microfasciculation: a morphological pattern in leprosy nerve damage Aims: To study Microfasciculation, a perineurial response found in neuropathies, emphasizing its frequency, detailed morphological characteristics and biological significance in pure neural leprosy (PNL), post‐treatment leprosy neuropathy (PTLN) and non‐leprosy neuropathies (NLN). Methods and results: Morphological characteristics of microfascicles were examined via histological staining methods, immunohistochemical expression of neural markers and transmission electronmicroscopy. The detection of microfasciculation in 18 nerve biopsy specimens [12 PNL, six PTLN but not in the NLN group, was associated strongly with perineurial damage and the presence of a multibacillary inflammatory process in the nerves, particularly in the perineurium. Immunoreactivity to anti‐S100 protein, anti‐neurofilament, anti‐nerve growth receptor and anti‐myelin basic protein immunoreactivity was found within microfascicles. Ultrastructural examination of three biopsies showed that fibroblast–perineurial cells were devoid of basement membrane despite perineurial‐like NGFr immunoreactivity. Morphological evidence demonstrated that multipotent pericytes from inflammation‐activated microvessels could be the origin of fibroblast–perineurial cells. Conclusions: A microfasciculation pattern was found in 10% of leprosy‐affected nerves. The microfascicles were composed predominantly of unmyelinated fibres and denervated Schwann cells (SCs) surrounded by fibroblast–perineurial cells. This pattern was found more frequently in leprosy nerves with acid‐fast bacilli (AFB) and perineurial damage while undergoing an inflammatory process. Further experimental studies are necessary to elucidate microfascicle formation.     

Diagnostic implications of podoplanin expression in peripheral nerve sheath neoplasms

By using the D2-40 antibody, we have observed podoplanin expression in Schwann cells and perineurial cells. Podoplanin expression has not been well characterized in peripheral nerve sheath tumors. Because neoplasms of neural crest lineage, including peripheral nerve sheath and melanocytic neoplasms, may share histologic and immunohistochemical characteristics, we evaluated podoplanin and S-100 expression in these lesions to determine the usefulness of podoplanin as a diagnostic marker. Diffuse podoplanin and S-100 expression was observed in 16 (76%) of 21 classical schwannomas, 6 (100%) of 6 cellular schwannomas, and 3 (75%) of 4 epithelioid malignant peripheral nerve sheath tumors (EMPNSTs). Podoplanin was expressed in 3 (7%) of 43 neurofibromas, 16 (21%) of 75 spindle cell MPNSTs (SMPNSTs), and 1 (10%) of 10 spindle cell melanomas but was absent in conventional melanoma. Only rare neurofibromas and SMPNSTs showed strong coexpression of podoplanin and S-100. These results suggest diffuse podoplanin expression or coexpression of podoplanin and S-100 is limited to schwannoma and EMPNST and may be useful in the evaluation of these neoplasms.     

Type VI collagen. In situ hybridizations and immunohistochemistry reveal abundant mRNA and protein levels in human neurofibroma, schwannoma and normal peripheral nerve tissues

Cutaneous neurofibromas contain an extensive extracellular matrix composed of collagenous and non-collagenous macromolecules. In this study, the expression of type VI collagen genes in cutaneous neurofibromas was examined by a combination of in situ hybridizations and immunohistochemistry. In situ hybridizations with a 32P-labeled human type VI collagen-specific cDNA revealed that the majority of cells within neurofibromas expressed the gene for alpha 2(VI) collagen chain. The number of cells expressing clearly detectable levels of alpha 2(VI) collagen mRNA was considerably higher than that of cells actively expressing the pro alpha 1(I) or pro alpha 1(III) collagen genes. The presence of type VI collagen epitopes within the neurofibromas was also demonstrated by immunostaining with specific polyclonal antibodies. The expression of type VI collagen genes in neural tissues was further examined by immunostaining of a benign schwannoma tissue specimen consisting of Schwann cells. The results indicated close association of type VI collagen epitopes with the neoplastic Schwann cells. Immunolocalization of type VI collagen epitopes within normal human peripheral nerve revealed pericellular staining of perineurial cells and Schwann cells, suggesting synthesis of type VI collagen by these cell types. These results suggest that the expression of type VI collagen gene is active in nerve-derived tissues, and that type VI collagen may be a major component of the extracellular matrix in neural connective tissues.     

PERINEURIAL CELL TUMOR AND THE SIGNIFICANCE OF THE PERINEURIAL CELLS IN NEUROFIBROMA

The authors attempted to clarify the exact cell components of neurofibroma by immunohistochemical and ultrastructural studies. Materials were randomly selected, 40 cases of neurilemoma and neurofibroma (-tosis) in addition to 2 cases of tumors composed exclusively of perineurial cells and three cases of normal peripheral nerve. The applied markers included antisera of S-100 protein for Schwann cells, blood coagulation factor XIIIa for endoneurial fibroblasts or perineurial cells, and laminin and collagen type IV for the basement membrane. S-100 protein was demonstrated only in normal or neoplastic Schwann cells, but not in perineurial cells. On the other hand, factor XIIIa was often recognized in endoneurial fibroblasts and perineurial cells, but not in Schwann cells. Neurofibroma was basically composed of a mixture of Schwann cells, perineurial cells, and endoneurial fibroblasts, the population of each type of cell differing according to the case and area within a given tumor. Perineurial cell tumor exclusively composed of perineurial cells, though rare, appears to be a definite entity, and its characteristic histological and ultrastructural features were described.