Electron microscopy in the diagnosis of malignant schwannoma

Electron Microscopy in an Oncologic Institution. Diagnostic Usefulness in Surgical Pathology

A retrospective survey of all electron microscopic (EM) examinations of surgical pathology specimens obtained at the Istituto Nazionale Tumori of Milan over a 5-year period (1981-1985) was carried out. During this time a total of 259 cases were examined: for 97 (38%) electron microscopy provided a substantial diagnostic contribution, whereas in 151 (58%) it confirmed the previous light microscopic diagnosis. In our experience, EM was most useful for diagnosing selected cases of cutaneous malignant melanoma predominantly metastatic, rhabdomyosarcoma, neuroblastoma and poorly differentiated neuroepithelial tumors and less helpful in the further analysis of cases of malignant mesothelioma, Ewing's sarcoma, leiomyosarcoma and fibrohistiocytic malignancies. In cases of well-differentiated neuroepithelial tumors, such as carcinoids, EM data was essentially confirmatory of (immuno)-histochemical findings.

Hemisacrectomy with preservation of the contralateral sacral nerve roots and sacroiliac joint for pelvic neurofibrosarcoma in a 7-year-old child: case report with 2-year follow-up

Neurofibrosarcoma is rare in the pediatric age group. A malignant tumor of the sacrum presents significant challenges, especially if the goals are to resect with wide and clean surgical margins and to achieve acceptable functional outcomes. The authors report a case of this rare tumor affecting the sacrum and sacral nerve roots of a 7-year-old girl and review the role of total hemisacrectomy sparing the contralateral sacral nerve roots and lumbopelvic reconstruction in the treatment of this disease. This patient is, to the best of the authors' knowledge, the youngest to be treated in this manner.

Organ-to-Cell-Scale Health Assessment Using Geographical Information System Approaches with Multibeam Scanning Electron Microscopy

This study combines novel multibeam electron microscopy with a geographical information system approach to create a first, seamless, navigable anatomic map of the human hip and its cellular inhabitants. Using spatial information acquired by localizing relevant map landmarks (e.g. cells, blood vessels), network modeling will enable disease epidemiology studies in populations of cells inhabiting tissues and organs.

Primary intraosseous schwannoma in tibial epiphysis with unique immunohistochemical phenotype: a case report

Schwannoma is a benign peripheral nerve sheath neoplasm of soft tissue that consistently demonstrates immunohistochemical staining for S100 protein. Intraosseous location of schwannoma is very uncommon. We report the first case of an intraosseous schwannoma located in the epiphysis of tibia in an adult patient. Radiologically, it mimicked a primary bone tumor and despite benign histological appearance, the tumor eroded cortical bone. Morphologically on routine stains and electron microscopy it has features of a schwannoma. But by immunohistochemistry, the tumor was positive for both desmin and S100 protein in the same region.

INI1-deficient tumors: diagnostic features and molecular genetics

Significant progress has been made in understanding the molecular genetic alterations involved in sarcomagenesis. Cytogenetic and molecular studies have identified nonrandom genetic abnormalities, including tumor suppressor gene inactivation. Mutations, deletions, and other somatic alterations in the tumor suppressor gene INI1 (hSNF5; SMARCB1), which encodes a subunit of the SWI/SNF chromatin remodeling complex, were first described in the malignant rhabdoid tumor of infancy. Since then, INI1 has also been implicated in the pathogenesis of additional tumor types including renal medullary carcinomas and epithelioid sarcomas and a subset of epithelioid malignant peripheral nerve sheath tumors, myoepithelial carcinomas, and extraskeletal myxoid chondrosarcomas. As varied as this group appears, they all show loss of INI1 protein expression, a propensity for rhabdoid cytomorphology, and sometimes other overlapping immunohistochemical and histologic findings. We will review the clinicopathologic features of these tumor types and emphasize the clinical utility of INI1 immunohistochemistry in differential diagnosis.

Prognostic factors for the malignant triton tumor of the head and neck

BACKGROUND

Malignant triton tumors are rare neoplasias consisting of a malignant peripheral nerve sheath tumor with additional rhabdomyoblastic differentiation. These tumors are highly aggressive and prognosis is poor. Our aim is to describe the outcome and to identify potential prognostic factors.

METHODS

From 1993 to 2005, 7 patients with a malignant triton tumor of the head and neck were treated at our institution. A literature search revealed another 46 published cases. All these cases were analyzed for outcome and prognostic factors.

RESULTS

Patients with primary tumors involving the nose and paranasal sinuses have better, patients involving the neck a poor prognosis. All other locations show an intermediate course. Complete surgical removal is of crucial importance. Additional radiation or chemotherapy show little effect.

CONCLUSION

Location of the primary tumor is a key factor for prognosis. Complete surgical removal is the only treatment associated with survival.

Glial FibriUary Acidic Protein (GFAP) Immunoreactivity in Peripheral Nerve Sheath Tumors

A spectrum of 24 benign and malignant nerve sheath tumors and 10 non-neural spindle-cell tumors were studied by light microscopy for the presence of glial fibrillary acidic protein (GFAP) immunoreactivity by the peroxidase-antiperoxidase (PAP) technique. In 8 cases, these results were compared to their electron microscopic appearances. Seventy percent (7 of 10) of benign schwannomas and 50% (4 of 8) of benign neurofibromas demonstrated focal to diffuse GFAP immunoreactivity. None of the malignant nerve sheath tumors nor any of the non-neural spindle-cell neoplasms contained demonstrable GFAP immunoreactivity. Similarly, no GFAP immunoreactivity could be detected in Schwann cells in normal peripheral nerves. The solitary benign schwannoma available for electron microscopic study demonstrated diffuse and abundant cytoplasmic intermediate filaments, and this tumor displayed diffuse and intense GFAP immunoreactivity. Two benign neurofibromas showed a more variable content of intermediate filaments ultrastructurally, and their GFAP immunoreactivity was variable. All five malignant nerve sheath tumors studied by electron microscopy displayed a variable complement of intermediate filaments; however, none of these tumors possessed GFAP immunoreactivity, suggesting that these intermediate filaments are either members of a different class of intermediate filaments or may perhaps represent "altered" GFAP not recognized by these antisera.

Description of a neural sheath tumor of the trigeminal nerve: immunohistochemical and electron microscopy study

CONTEXT

Malignant neural sheath tumors of the trigeminal nerve affecting the nasal cavity and the paranasal sinuses are extremely rare. With conventional optical microscopy, their identification is difficult, and it is necessary to confirm them by means of electron microscopy and immunohistochemical techniques.

CASE REPORT

The patient was a 41-year-old woman with a ten-month progressive history of pain followed by painful edema in the left facial region, and with symptoms of bleeding, secretion and nasal obstruction. Studies with imaging methods suggested the presence of an expansive process in the left nasal and paranasal cavities. In the biopsy, the histopathological findings from optical microscopy were suggestive of a tumor of neural origin in the trigeminal nerve. Immunohistochemical and electron microscopy studies confirmed that it was a malignant tumor of the neural sheath of the trigeminal nerve. We describe the clinical, radiological, and histological features of this tumor and review the literature.

Divergent differentiation in malignant soft tissue neoplasms: the paradigm of liposarcoma and malignant peripheral nerve sheath tumor

In tumors clonality does not always translate into morphologic uniformity. While most sarcomas exhibit only one line of histologic differentiation, a minority may display a strikingly diverse phenotype in addition to the main lineage. This phenomenon not only presents a diagnostic problem but also raises questions about the commitment of tumor cells toward a specific phenotype. Among sarcomas, malignant peripheral nerve sheath tumor (MPNST) and dedifferentiated liposarcoma are two entities in which divergent differentiation is a relatively frequent event. Diagnostically it is crucial to recognize the "primary" sarcoma in such tumors correctly and distinguish it from the "secondary" divergent elements. The presence of the latter could be the first morphologic clue to a specific sarcoma type. Even though it may be difficult to explain the pathogenesis of divergent differentiation, divergence still illustrates that the phenotype of a tumor cell is not set in stone but can be modulated or switched by a number of factors.

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.

Isolated peripheral neurilemoma attached to the tendon of the flexor digitorum longus muscle

Neurilemomas are benign tumours arising from peripheral nerves with a Schwann cell sheath. They are normally painless and slowly growing, rarely causing motor disturbances. Neurilemomas are most common in the cranial nerves, in the trunk, the upper and lower extremities, but may appear anywhere. Especially rare are neurilemomas of the lateral peroneal nerve in the region of the fibular head and in the foot. We present the first detailed report of a neurilemoma localized between the Achilles tendon and the flexor digitorum longus muscle with separation of the tumour from the tibial nerve.

Pediatric neurofibrosarcoma

BACKGROUND/PURPOSE

Neurofibrosarcoma is rare in children, and the natural history and prognostic factors are not well described. The authors present a 57-year review of their experience.

METHODS

The charts of children with neurofibrosarcoma were reviewed retrospectively. Statistical analysis was performed using the Chi2 and unpaired t tests.

RESULTS

From 1944 to 2001, 38 patients under the age of 21 were diagnosed with neurofibrosarcoma. Twenty-two were boys. The average age at diagnosis was 13.8 years (range, 3 to 19.9 years). Nineteen patients (50%) had neurofibromatosis. The tumor site was as follows: extremity, 19 patients; trunk, 9 patients; head and neck, 7 patients; and retroperitoneum, 3 patients. The average tumor size was 10 cm. The margins after resection were as follows: grossly positive, 9; microscopically positive, 5; negative, 21; and unknown, 3. Patients with positive margins had a 22% survival rate, whereas those with negative or unknown margins had a 34% survival rate. Thirty-two patients achieved a complete response, 2 a partial response, and 4 progressed while on therapy. Twenty-six patients relapsed after a complete response (11 local, 10 distant, 5 both). Of the 15 patients with a distant relapse, 73% (11) relapsed in the lung. Twelve (32%) patients survived with an average follow-up of 14 years (range, 0.3 to 28 years). Nine patients were treated with chemotherapy, 9 with radiation, and 9 with both chemotherapy and radiation. Outcome was not significantly affected by gender, presence of neurofibromatosis, site, margin, or use of adjuvant therapy.

CONCLUSION

Neurofibrosarcoma remains a rare disease in children with insufficient contemporary numbers to assess efficacy of therapy. Prognosis remains poor with a high incidence of relapse, particularly in the lungs, suggesting that more aggressive therapies to control both local and distant relapses are needed.

Malignant triton tumor of the nasal cavity

BACKGROUND

Malignant triton tumor is usually an aggressive sarcoma consisting of a malignant schwannoma with rhabdomyoblastic differentiation. However, malignant triton tumor of the nasal cavity is very rare.

METHODS

A case report of a 38-year-old woman with polypoid mass, which bled easily in the right nasal cavity, and nasal obstruction is presented with a review of the literature pertaining to this unusual case.

RESULTS

The malignant triton tumor was treated with wide surgical excision followed by radiation therapy. Histopathological diagnosis of the malignant triton tumor was made on the surgical specimen. The patient's postoperative course was unremarkable, and follow-up at 5 years reveals no evidence of disease.

CONCLUSIONS

A malignant triton tumor in the nasal cavity is a rare disease. Head and neck surgeons should recognize the possibility of malignant triton tumor occurring in the nasal cavity.

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

AIMS

The diverse histological features in malignant peripheral nerve sheath tumours (MPNSTs) associated with NF-1 were investigated by immunohistochemical and electron microscopic analysis. Our study is focused on the differentiation of the tumour cells in the heterogeneous components.

METHODS AND RESULTS

Twenty-three cases were classified as conventional type, epithelioid type, anaplastic type, and heterogeneous type, and divided into three groups by the presence of S100 protein (S100)-positive cells in each tumour; Group A was defined as having >50% S100+ cells, Group B as having <50%, and Group C as cases with no positive cells. To investigate the differentiation of the tumour cells, the morphology and immunoreactivity for neural or mesenchymal markers among the three groups were compared. For the identification of Schwannian, perineurial, and endoneurial differentiation, markers for S100, EMA and CD34 were used, respectively. In three tumours of the Group A type, there were no cases showing differentiation towards perineurial or endoneurial cells, or formation of heterogeneous components. In nine tumours of the Group B type, one tumour expressed EMA and CD34, suggesting probable perineurial and/or endoneurial differentiation. One tumour showed rhabdomyoblastic differentiation. Three tumours showed cartilaginous or osteogenic differentiation, and one of the three also showed a focal vascular differentiation. The surrounding areas of the heterogeneous components were composed of mixed S100+ cells and S100- cells. S100- cells in the areas were positive for CD34 in one case. In 11 tumours of Group C type, one tumour expressed EMA and CD34 suggesting perineurial and/or endoneurial cell differentiation. Three tumours showed rhabdomyoblastic differentiation. The tumour cells around the heterogeneous components in the three cases were negative for EMA and CD34.

CONCLUSION

Our results suggest that tumour cells differentiating to Schwann cells are not the only component of MPNSTs. Furthermore, tumour cells other than Schwann cells are largely related to the formation of the heterogeneous components in MPNSTs associated with NF-1.

Malignant triton tumor of the head and neck: A case report and review of the literature

BACKGROUND

Malignant triton tumor (MTT) is a relatively rare, aggressive tumor comprised of both malignant schwannoma cells and malignant rhabdomyoblasts. Because MTT frequently arises in the head and neck, the otolaryngologist must be aware of the nature of the tumor and its response to various treatment modalities.

METHOD

This article reviews the treatment and outcome of all reported cases of MTT arising in the head and neck.

CONCLUSIONS

Although statistical analysis is limited by the short duration of follow-up of many patients, complete tumor resection appears to carry an improved chance of survival. Adjuvant radiation and chemotherapy may also improve survival, although a benefit of these therapies was not well demonstrated in this small series.

Malignant peripheral nerve sheath tumor of bone in children and adolescents

Malignant peripheral nerve sheath tumor (MPNST) of bone is a rare entity. We have examined three lesions that fit standard histopathologic criteria for MPNST of soft tissues but that arose in the skeleton of three children aged 6 to 13 years. None was affected by neurofibromatosis 1 (NF1). Histologic features typical of MPNST included spindle cells with comma-shaped nuclei, tactoid bodies, nuclear palisading, hyaline bands, and schwannoma-like and curlicue foci. Epithelioid foci were seen in two cases, and heterologous differentiation in one. Immunohistochemistry revealed positivity for S-100 (1 positive/3 tested), vimentin (3/3), glial fibrillary acidic protein (2/3), CD34 (1/1), and CD68 (1/2). Studies for CD99 (0/3), epithelial membrane antigen (0/3), cytokeratin (0/3), CD57 (0/3), and HMB-45 (0/2) were negative. Ultrastructural findings in one of two cases examined included interlacing, attenuated cytoplasmic processes, microtubules, and rare dense-core granules. We conclude that MPNST may arise as a primary bone neoplasm in children without NF1.

Primary intraosseous malignant peripheral nerve sheath tumor: a case report and review of the literature

Primary intraosseous malignant peripheral nerve sheath tumors (MPNST) are exceptionally rare; the case reported here represents the first documented example occurring in the spinal column. The tumor arose in the second cervical vertebra of a forty year old woman of Asian origin. She had no stigmata of von Recklinghausen's disease (VRD). Plain radiographs and magnetic resonance imaging showed an osteolytic lesion within the expanded body of the vertebra. Histology revealed spindle-shaped tumor cells with nuclei showing pleomorphism, pallisading and mitotic activity. The cells stained positively for S-100 protein. The patient underwent stabilisation of the cervical spine and tumor excision as a two-stage procedure. She died of pulmonary metastases one year later. We have reviewed the literature on the pathology of these tumors.

Subdiaphragmatic and intrathoracic paraspinal malignant peripheral nerve sheath tumors: a clinicopathologic study of 25 patients and 26 tumors

BACKGROUND

To determine the effects of anatomic site on the presentation and diagnosis of malignant peripheral nerve sheath tumors (MPNSTs) and on the treatment and outcomes of the patients, the authors initiated a study of these tumors at different sites. An earlier report described MPNSTs of the buttock and lower extremity, and the current series analyzes those presenting at intrathoracic (IT) and subdiaphragmatic (SD) paraspinal sites.

METHODS

The authors reviewed data on patients with paraspinal MPNSTs who were seen at Memorial Hospital during the period 1960-1995 and for whom histologic slides were available. Various clinicopathologic parameters and their effects on patient outcomes were examined.

RESULTS

Twenty-five patients with 26 tumors were evaluated. Seven tumors were IT and 19 were SD; 60% of the patients had neurofibromatosis type 1 (NF1). Most patients presented with pain, and a diagnostic delay (of 3 months to 2 years) was often noted. Mean tumor sizes for SD and IT tumors were 14.3 cm and 6.6 cm, respectively. Most MPNSTs were composed of spindle cells in fascicles. Twenty-seven percent exhibited divergent differentiation. Twenty-four tumors were high grade, and a low grade component was identified in 8 tumors. Surgical resection was attempted for 23 tumors (88%), but complete resection was achieved in only 6 cases (23%). Eighty percent of the patients died of their tumors, 2-year and 5-year survival rates were 35% and 16%, and median survival was 8.5 months. Significant prognostic factors were tumor size <5 cm, the presence of a low grade component, and complete tumor resection.

CONCLUSIONS

Paraspinal MPNSTs have more aggressive behavior than peripherally located tumors, mainly because of the difficulty encountered in resecting them completely. Prognoses of patients with MPNST at this site appear to be affected by resection status, tumor size, and tumor grade.

Juxta-adrenal malignant schwannoma

A case of malignant schwannoma occurring in an 11-year-old boy is described. To our knowledge, this is the third case of malignant juxta-adrenal schwannoma reported in the literature. It was misdiagnosed at the onset of the disease as a post-traumatic renal hematoma. Angiography revealed that the tumor derived its blood supply from collateral vessels of the aorta, splenic, and left gastric arteries. An analysis of the diagnosis, clinical course, and prognostic factors of this rare tumor is performed.

A case of von Recklinghausen's disease with bilateral pheochromocytoma-malignant peripheral nerve sheath tumors of the adrenal and gastrointestinal autonomic nerve tumors

A 48-year-old man with neurofibromatosis type 1 presented with chest pain, paroxysmal hypertension, tachycardia, and progressive respiratory insufficiency. Clinical investigation displayed calcified tumors in the anterior mediastinum and pararenal region. Histological examination at autopsy revealed composite tumors consisting of pheochromocytoma and malignant peripheral nerve sheath tumor (MPNST) at two sites: the left adrenal gland and the region surrounding the inferior vena cava, probably corresponding to the right adrenal gland. The MPNST component showed a varied histological appearance, including hyalinized bands with polygonal cells, a cartilaginous and myxoid stroma, a hemangiopericytomatous architecture, and a fibrosarcomatous structure, which suggested osteosarcoma, chondrosarcoma, angiosarcoma, and fibrosarcoma, respectively. In addition, based on the ultrastructural findings, the gastrointestinal tract was involved with mesenchymal tumors showing neurogenic differentiation. These lesions suggest the divergent cellular differentiation of neural crest-derived cells to mesenchymal elements as well as neuroectodermal neoplasms.

Malignant peripheral nerve sheath tumor with prominent intracytoplasmic vacuolation: report of a case

A case of malignant peripheral nerve sheath tumor with uncommon features is reported. A mass was noted in the left thigh of a 16 year old man. Histologically, most areas of the tumor exhibited the typical appearance of malignant peripheral nerve sheath tumor, but some tumor cells had rounded nuclei and cytoplasm, resembling an epithelioid pattern. It was noted that some rounded tumor cells showed prominent intracytoplasmic vacuolation. Immunohistochemically, almost all of the tumor cells, including the rounded and vacuolated ones, were positive for S-100 protein and vimentin. Electron microscopic study revealed well-developed cytoplasmic processes, intracytoplasmic intermediate-sized filaments, basement lamina formation and extracellular long-spacing collagens. These findings were compatible with those of Schwann cell differentiation. Moreover, ultrastructurally, the vacuolated spaces contained a few granular materials and were derived from the dilatation of the rough endoplasmic reticulum. It is speculated that intracytoplasmic vacuolation in malignant peripheral nerve sheath tumor would be caused by degeneration of the tumor cells.

Malignant schwannoma with rhabdomyoblastic and melanocytic differentiation

This is the first case report of an unusual malignant tumor with components of malignant schwannoma, rhabdomyosarcoma, and melanoma, occurring in an adult. The tumor was observed in the left temple in a 35-year-old man without von Recklinghausen's disease. The possible derivation of this tumor from primitive neuroectodermal cells is discussed.

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.

Peripheral nerve sheath differentiation in malignant soft tissue tumours: an ultrastructural and immunohistochemical study

Thirteen soft tissue sarcomas with ultrastructural evidence of nerve sheath differentiation were investigated by immunohistochemistry. Three arose in a major nerve or nerve trunk and four patients had von Recklinghausen's neurofibromatosis. Ultrastructurally, 10 cases showed variable differentiation towards Schwann cells, two resembled perineurial cells and one tumour had features suggestive of both cell types. Immunostaining for S-100 protein was positive in eight Schwann cell tumours, negative in the other two Schwann cell tumours and negative in those with perineurial-like cells. No cases demonstrated epithelial membrane antigen, so that the existence of perineurial cells in malignant nerve sheath tumours remains immunohistochemically unsubstantiated; it may be that the perineurial-like cells are merely incompletely differentiated Schwann cells, with nerve sheath differentiation manifesting a continuous spectrum. Leu 7 was detected in four Schwann cell tumours, three of which were ultrastructurally well differentiated. Cytokeratin and desmin were demonstrated only in an undifferentiated pleomorphic area of one Schwann cell tumour. Electronmicroscopy can aid diagnosis by revealing nerve sheath differentiation in malignant soft tissue tumours without demonstrable S-100 protein.

Maxillofacial malignant peripheral nerve sheath tumours

The clinical and pathological features of 7 patients with MPNST in the maxillofacial area are reviewed. They occurred in five men and two women; ages ranged from seven to eighty years. The parotid area and infratemporal fossa were the commonest sites (two cases each), followed by the lower lip, cheek and central mandible (one case each). Two had the antecedent of an excised neurofibroma, one with von Recklinghausen's disease and radiotherapy, that had recurred many times. Pathological slides were revised. Immunohistochemistry with S-100 protein was positive in 6 of 7 cases; electron microscopy confirmed the diagnosis in 3 cases. None showed divergent differentiation. Surgical treatment was performed in all, with or without radiotherapy. Surgical margins were positive in five cases. Recurrence took place in six and was multiple in three. Surgical salvage of the local recurrences produced satisfactory results in 3 of the 6 cases. One patient developed lung metastasis.

Synovial sarcoma: an immunohistochemical and ultrastructural study

Thirty-nine primary synovial sarcomas (15 biphasic, 24 monophasic), and 19 metastatic synovial sarcomas were studied with a battery of antibodies directed to keratin, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA), vimentin, desmin, muscle-specific actin, smooth muscle actin, S-100 protein, Leu-7, chromogranin A, laminin, collagen IV, Ulex europaeus agglutinin I (UEAI), and the HMB-45 antimelanoma antibody. Twenty-two primary and 18 metastatic synovial sarcomas were also examined by electron microscopy. Epithelial and/or spindle cells in every biphasic tumor, primary and metastatic, reacted for keratin and EMA, but only six primary tumors (five biphasic and one monophasic) showed weak reactivity for CEA which, in the biphasic tumors, was confined to the epithelial component. Of the monophasic tumors, 15 primary (63%) and four metastatic (25%) stained for keratin, whereas seven primary (29%) and two metastatic (13%) tumors reacted for EMA. Only one primary monophasic synovial sarcoma stained for CEA. Tumors that stained for EMA or CEA also stained for keratin which is, therefore, the most useful epithelial marker. Immunostaining for epithelial markers, UEAI, collagen IV, and laminin serves to delineate the epithelial component when it is obscure in routine sections. Electron microscopy facilitates the diagnosis when epithelial markers are not expressed and aids in separating monophasic synovial sarcomas from other sarcomas that they resemble by light microscopy.

Malignant schwannoma arising in the intracranial trigeminal nerve. A report of an autopsy case and a review of the literature

An autopsy case of malignant schwannoma arising in the intracranial trigeminal nerve is reported. The tumor involved the right cerebellopontine angle of the brain stem in an 18-year-old man. The spindle-shaped tumor cells with eosinophilic cytoplasm proliferated in fascicles and exhibited hypercellularity, pleomorphism, increased mitotic activity and invasive growth. Ultrastructurally, interdigitating cytoplasmic processes and a few fragmented basal lamina-like structures were observed. Immunohistochemically, some tumor cells were reactive with conventional anti-S-100 protein antibody, but negative for beta subunit. Most tumor cells were positive for alpha subunit of S-100 protein. This is the eighth reported case of malignant schwannoma arising in the intracranial trigeminal nerve.

Primary omental tumor with ultrastructural features of cellular schwannoma and absence of S-100 antigen reactivity

We report a primary well-delimited, large mesenchymal omental neoplasm which appeared in a 58 year old man without neurofibromatous traces. The histological and ultrastructural features were consistent with a Schwann cell origin. However, repeated immunohistochemical reactions failed to demonstrate protein S-100 antigen reactivity in the neoplastic cells, the latter only expressing vimentin. The differential diagnosis with hemangiopericytoma is proposed.

Intraspinal pigmented schwannoma with malignant progression

A case with recurrent pigmented intraspinal tumour with malignant progression is presented. The primary tumour grew around the nerve roots T9 and T10, was attached to dura and infiltrated the vertebral bone tissue. On light microscopy it was comprised of monomorphic cells with large amount of cytoplasmic pigment and many large pigmented globoid bodies. Mitoses were not observed. On electron microscopy, in addition to cytoplasmic melanosomes of regular size, macromelanosomes were numerous. The tumour cells were surrounded partially by basement membrane like material. On these bases a histological diagnosis of benign pigmented tumour of neural crest origin was suggested (a possible pigmented meningioma or pigmented schwannoma). The patient got a recurrence one year after the primary operation. Biopsy from the re-operation showed histologically the same type of tumour with more pleomorphic cells. Subsequently, the tumour grew progressively and metastases were observed in the lungs and in the skin. The patient died two years after the primary operation. The malignant progression of the tumour and other reports on similar tumours was most consistent with a diagnosis of malignant pigmented schwannoma and this was confirmed later on with immunohistochemical staining showing positive staining for basement membrane components, collagen type IV and laminin as well as a positive staining for S-100 protein. The present findings show that despite benign histological features these tumours can behave very aggressively and stress the need of more information on this type of tumour.

Malignant epithelioid schwannoma: a light microscopic and immunohistochemical study

Malignant epithelioid schwannoma is a rare variant of malignant nerve sheath tumor that can be confused with both other neuroectodermal neoplasms and carcinomas. The light microscopic and immunohistochemical findings of a malignant epithelioid schwannoma arising in the mandibular region of a 27-year-old female are described. The differential diagnosis of this unusual neoplasm from malignant melanoma and poorly differentiated carcinoma is discussed.

Heterogeneity of malignant schwannomas

Six malignant schwannomas were studied by electron microscopy and immunohistochemistry for S-100 protein at the light and electron microscopic levels to clarify the nature of the tumor cells. Three tumors (group A) were composed of poorly differentiated tumor cells and showed no immunoreactivity for S-100 protein. One tumor (group B) was composed of perineurial cells that were S-100 protein-negative. Two tumors (group C) consisted of both Schwann cells and fibroblastic cells like neurofibromas, and only the former were found to contain S-100 protein. Thus, this study showed the heterogeneous nature of the malignant schwannomas and suggested that these tumors might arise from multipotential Schwann cells or different cellular components of peripheral nerve or primitive cells.

Melanoma arising in a spinal nerve root. Case report

Melanotic neoplasms of the spinal nerve root are rare but well-documented occurrences. The authors report the case of a 68-year-old woman with a malignant melanotic neoplasm containing premelanosomes and melanosomes and lacking a basal lamina. This tumor was found in a lumbar nerve root and is believed to represent an instance of a primary melanoma arising in a spinal nerve root. The differential diagnosis of pigmented lesions of spinal nerve root includes melanoma, pigmented nerve sheath tumor, blue nevus, melanotic clear-cell sarcoma, and meningeal melanocytoma. Surgeons should be aware of the potential for encountering unexpected malignant lesions involving spinal nerve roots.

Infravesical obstruction caused by a retrovesical malignant schwannoma

A 77-year-old male presented himself with acute urinary retention, and a history of infravesical obstruction. Cystourethroscopy failed to show the obstruction. A malignant schwannoma (MS) causing impression in the bladder was removed through a laparotomy. Postoperatively there were no urologic symptoms, and the urodynamic investigations had changed to normal.

Reversible endoneurial changes after nerve injury

Endoneurial changes in the rat sciatic nerve were studied during Wallerian degeneration and subsequent regeneration. After total axotomy two different experimental models were used. In the first the cut ends of the sciatic nerves were left free to allow reinnervation. In the second model the distal end of the transected nerve was sutured to the adjoining muscle to prevent regeneration. Within 2 weeks after the axomoty, a Wallerian type of degeneration was seen with axonal destruction and phagocytosis of myelin sheaths. After 4 weeks endoneurial fibroblastic cells formed circular structures around the Schwann cell columns, i.e., the bands of Buengner in both groups. These fascicle-like structures became more pronounced in the non-regenerating nerves up to 8 weeks, while during reinnervation the cellular reaction in the endoneurium nearly disappeared within this time. Ultrastructurally, the endoneurial fibroblast-like cells showed marked phagocytotic activity and also fragments of basement membrane on their surface. The appearance of thin (25-30 nm in diameter) collagen fibrils closely related to the basement membrane was noted around the bands of Buengner, as well as the appearance of an amorphous extracellular gap between the newly synthetized thin collagen fibrils and normal endoneurial collagen (50-60 nm). The reversible endoneurial compartmentation seems to be important for maintaining the nerve structure, serving as a support for axonal regeneration in addition to the bands of Buengner.

Malignant triton tumour in the cerebellopontine angle. Report of a case

A report is given of a 24-year-old woman with a malignant cerebellopontine angle tumour, which appeared to have arisen from the 8th nerve sheath. It had a predominantly fasciculated, spindle-cell, Schwannoma-like structure, but also included rhabdomyoblastic elements and a diagnosis of malignant triton tumour is proposed. The patient did not have Von Recklinghausen's disease.

Malignant schwannoma of the mandible

A case of malignant schwannoma occurring in the mandible of a 76-year-old Japanese woman is presented. Results of the gross examination are described as well as the surgical procedure. Details of the staining techniques for examination of the biopsy specimen are given. The histopathological findings are mentioned including those obtained from radiographic, microscopic, and electron microscopic examination. A discussion of the disease and of its difficulty of diagnosis follows.

Superficial spreading malignant melanoma with neurosarcomatous metastasis

A case of neurosarcomatous nodal metastasis of superficial spreading malignant melanoma, without primary site desmoplasia or sarcomatous changes, is reported. Of particular interest regarding the metastasis are: the ultrastructural demonstration of numerous cytoplasmic microtubules, absence of premelanosomes, intense immunohistochemical reaction with S-100 protein antibody, and the presence, at the light microscopic level, of extranodal fibrosis. The primary lesion shows a pre-existing benign nevus and features suggestive of lamellar fibroplasia. The origin and histogenesis of melanocytic desmoplasia, in the context of a neural crest progenitor cell, and of lamellar fibroplasia, are discussed.

Malignant schwannoma with a rhabdomyoblastic component, a so-called triton tumor. A clinicopathologic study

Triton tumors, malignant schwannomas with a rhabdomyoblastic component, are rare. This article reports the clinical course, therapeutic approach, and histopathologic aspects of three cases. Immunoperoxidase staining for the Schwann's cell marker S-100 protein and for the skeletal muscle proteins desmin, myosin, and myoglobin proved to be useful for diagnosis. The clinical histories of 24 previously reported cases are analyzed, and the therapeutic possibilities are discussed.

Epithelioid malignant schwannoma. A study of 14 cases

We report a light and electron microscopic, immunohistochemical, clinical and prognostic study of 14 patients with epithelioid malignant schwannoma. In 8 patients the tumour involved a major nerve. The tumours were rather small in most instances, the largest diameter being less than 5 cm in 7 cases. Light microscopically, they showed highly cellular areas of epithelioid, polygonal or rounded cells characteristically forming cords and rows and arranged in nodules of varying size. Spindle cell sarcoma areas as in classical malignant schwannoma were seen in 9 cases, and neurofibromatous areas in one case. Four cases were entirely epithelioid in appearance. Electron microscopically the epithelioid tumour cells showed nuclei with mostly even contours containing one or two trabecular or reticular nucleoli, cytoplasmic projections, intra-cytoplasmic myelin-like figures, intercellular junctions and discontinuous, sometimes multilayered external lamina material. The ultrastructural findings indicate that epithelioid malignant schwannoma is a tumour of neural crest derivation having features of Schwann cell differentiation. Immunohistochemically, S-100 protein was demonstrated in 7 tumours and neuron specific enolase in 3. There was a female predominance, 9/14, and a median age of 38.5 years (range 17-74). The extremities, including the hip and shoulder regions, were the most common sites, 12/14. The tumour proved highly malignant; 9 of 14 patients were dead at the time of follow-up and a high incidence of metastasis (7 of 14) was observed.

Malignant peripheral nerve sheath tumors. A clinicopathologic study of 120 cases

A review was done of 120 cases of malignant peripheral nerve sheath tumor (MPNST) seen during a 71-year period. Of the 120 patients, 52 were males and 68 were females with a mean age at diagnosis of 35.3 years; 12 patients were younger than 20 years. The series included 62 (52%) patients with neurofibromatosis, 13 (11%) with postradiation sarcomas, and 19 (16%) with metaplastic foci. The incidence of MPNST arising in neurofibromatosis was 4.6% in the current series and 0.001% in the general clinic population. Tumors greater than 5 cm and the presence of neurofibromatosis adversely affected the prognosis (P less than 0.05). When both features were present, survival was greatly decreased. Patients with tumor in the extremities did better than those with head or neck lesions. Metaplastic foci or previous radiation at the tumor site did not alter the prognosis. Each tumor was graded 1 to 4 on the basis of cellularity, pleomorphism, mitotic index, and necrosis. No significant correlation was noted between survival and either grade or mitotic rate. Survival was improved when total rather than subtotal resection was done. This was most marked in patients with a small lesion, which may reflect the difficulty in adequately excising large tumors. Adjuvant radiation or chemotherapy did not appear to affect survival. The MPNST is an aggressive uncommon neoplasm, and large tumor size, the presence of neurofibromatosis, and total resection are the most important prognostic indicators.