Malignant schwannoma: a light microscopic and ultrastructural study

Retroperitoneal malignant schwannoma in a child

Retroperitoneal malignant schwannomas are extremely rare. Only a few cases have been reported, only one of which occurred in a child. We herein report a case of retroperitoneal malignant schwannoma in a 2-year-old boy who presented with a painless mass in the right lumbar region. The mass had gradually enlarged during a 1-year period, and it was about the size of the patient's fist at the time of consultation. Whole-abdomen computed tomography revealed a space-occupying lesion in the retroperitoneum infiltrating from the L1 to L4 spinal canal. A preoperative diagnosis of a retroperitoneal tumor was made, and complete tumorectomy was performed. Postoperative pathological examination showed a malignant schwannoma. The tumor recurred 1 month after the first operation, and a second complete excision was carried out; the postoperative pathologic examination findings were similar to the previous findings. The patient recovered well and continued to undergo close follow-up.

Soft tissue tumors of the anorectum: rare, complex and misunderstood

Anorectal soft tissue tumors are uncommon and often present both diagnostic and therapeutic challenges. Although many of these tumors are identified with imaging performed for unrelated reasons, most present with nonspecific symptoms that can lead to a delay in diagnosis. Historically, radical surgery (abdominoperineal resection) has been the mainstay of treatment for both benign and malignant anorectal soft tissue tumors. However, a lack of proven benefit in benign disease along with changes in technology has called this practice into question. In addition, the role of radiation and/or chemotherapy remains controversial. In this manuscript, we review the history and current status of anorectal soft tissue tumor management, with a particular focus on challenges in optimizing survival.

Use of electron microscopy to classify canine perivascular wall tumors

The histologic classification of canine perivascular wall tumors (PWTs) is controversial. Many PWTs are still classified as hemangiopericytomas (HEPs), and the distinction from peripheral nerve sheath tumors (PNSTs) is still under debate. A recent histologic classification of canine soft tissue sarcomas included most histologic types of PWT but omitted those that were termed undifferentiated. Twelve cases of undifferentiated canine PWTs were evaluated by transmission electron microscopy. The ultrastructural findings supported a perivascular wall origin for all cases with 4 categories of differentiation: myopericytic (n = 4), myofibroblastic (n = 1), fibroblastic (n = 2), and undifferentiated (n = 5). A PNST was considered unlikely in each case based on immunohistochemical expression of desmin and/or the lack of typical ultrastructural features, such as basal lamina. Electron microscopy was pivotal for the subclassification of canine PWTs, and the results support the hypothesis that canine PWTs represent a continuum paralleling the phenotypic plasticity of vascular mural cells. The hypothesis that a subgroup of PWTs could arise from a pluripotent mesenchymal perivascular wall cell was also considered and may explain the diverse differentiation of canine PWTs.

Recurrent retroperitoneal Schwannomas displaying different differentiation from primary tumor: case report and literature review

Background

Retroperitoneal Schwannomas are uncommonly found in the retroperitoneum and few of them show malignant transformation and invasion. Local recurrence are common in malignant Schwannomas with very few reports of tumor distinct differentiation at recurrences.

Case presentation

We report here a rare case of retroperitoneal schwannoma with multiple origins from retroperitoneum and pelvic wall. Pathological examination confirmed the case as a schwannoma with malignant transformation. Radical dissection of the tumors along with the sacrifice of adjacent sigmoid colon and left kidney failed to provide a cure for this patient. Due to tumor recurrence, a second and a third surgery of radical excision were performed 6 months and 17 months later after the first surgery, respectively. Histopathologic analysis identified that the recurrent tumors were different from the original schwannoma because of their smooth muscle-like differentiation.

Conclusion

Malignant schwannomas are uncommon sarcomas with a high incidence of local recurrence. Distinct immunohistochemical staining results of the tumors at recurrence indicate their potential of smooth-muscle like differentiation. Radical excision of the tumors may provide benefit for their local recurrences.

Epithelioid Schwannoma: Diagnosis by Electron Microscopy

The clinical, gross, and light microscopic features of two epithelioid tumors were not typical of either benign or malignant schwannoma. Both tumors displayed long, enveloping cytoplasmic processes that were outlined by layers of discrete basal lamina. Long-spaced collagen was found in one case. These well-developed electron microscopic features are those that are commonly encountered in benign Schwann cell tumors. Although one patient died postoperatively, the other is alive and well 12 months after surgery. The extent to which ultrastructural data can have an impact on the evaluation of Schwann cell tumors is unknown but requires further study.

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.

Malignant trigeminal schwannoma extending into the anterior skull base

Malignant schwannomas are rare tumours that seldom grow in the head and neck and their occurrence is even rarer in patients not affected by neurofibromatosis. The authors report a 40 year old woman with a left trigeminal malignant schwannoma (arising from V2), involving the infratemporal fossa and subsequently extending into the maxillary, sphenoid and ethmoidal sinuses, the orbit, and the intracranial compartment. Given the complex location of this tumour, the patient initially underwent radiation treatment; however due to a poor response to this form of treatment as well as disease progression, surgical resection requiring a combined Neurosurgical, ENT and Plastic Surgery was recommended. The planned operation included sacrificing the internal carotid artery and cavernous sinus, ipsilateral orbit exenteration and reconstruction with a free flap from the latissimus dorsi muscle. In this report, we discuss the sporadic occurrence of these tumours, the histo-pathological features and the management strategy along with a review of the literature.

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.

Laparoscopic resection of a retroperitoneal schwannoma behind the lesser omental sac

Most schwannomas occur in the head, neck, or limbs with a few cases occurring in the retroperitoneal space. In benign schwannoma occurring in the retroperitoneal space, tumors are most commonly located near the adrenal gland. Herein, we report on a 55-year-old Japanese man with benign schwannoma (6x4 cm) behind the lesser omental sac, which was removed under laparoscopy. Non-functioning neurogenic tumor was suspected as a differential diagnosis by computed tomography, ultrasonography, and magnetic resonance imaging, and the patient underwent laparoscopic resection of the tumor. Histologically, the resected tumor was diagnosed as benign schwannoma. The patient was discharged from our hospital on the tenth postoperative day without any complications. A laparoscopic surgical technique is safe and feasible for the diagnosis and treatment of retroperitoneal benign tumors such as schwannoma.

Peripheral tumors of the intercostal nerves

Fewer than 10% of primary neural tumors of the chest originate peripherally from intercostal nerves; most neural tumors of the chest arise in the mediastinum. Most patients with primary tumors of the intercostal nerve are asymptomatic. We report a case of neurilemmoma arising from an intercostal nerve in a woman seen for severe pain in the chest wall. Resecting the tumor relieved the pain. Recent medical literature describing peripheral tumors of thoracic nerves is reviewed.

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.

Two schwannomas presenting as lumps in the same breast

A case of two benign schwannomas of the right breast in a 25-yr-old woman is presented, including the use of fine-needle aspiration and biopsy diagnosis. A review of the literature did not reveal any such duality in the same breast. The tumors were made of clusters of spindle cells on cytological material. The final diagnosis was established through histological examination of the excised masses.

Malignant schwannoma located in the retroauricular region

There have been no reports about malignant Schwannoma located retroauricularly in the medical literature we reviewed. Malignant Schwannoma is a very malignant tumor, which is rare. For diagnosis, microscopic and immunohistochemical studies are needed. It is often seen together with neurofibromatosis. The prognosis is very poor and the only available treatment is surgical excision. Although it is known that both radiotherapy and chemotherapy are not effective, we achieved good outcome with this combination applied postoperatively.

Malignant peripheral nerve sheath tumors. A clinicopathologic study of 28 cases

BACKGROUND

In order to improve management, the files and tissue sections of 28 cases of malignant peripheral nerve sheath tumors (MPNST) diagnosed at the University of Virginia Health Sciences Center between 1960 and 1990 were reviewed.

METHODS

Clinical data tabulated included age, sex, race, the presence or absence of von Recklinghausen neurofibromatosis type 1 (NF-1), tumor size, tumor location, type of treatment, and status of surgical margins. Pathologic study included assessment of mitotic rate, divergent differentiation, cellular atypia, necrosis, and vascular reaction.

RESULTS

The median disease-free survival time was 11 months, and the median overall survival time was 44 months. Overall survival and disease-free survival were significantly influenced by patient age, tumor location, tumor size, extent of surgery, and quality of margins. Patients with a family history of neurofibromatosis also had better disease-free survival. None of the other clinical variables correlated with survival.

CONCLUSIONS

The authors recommended that patients with NF-1 be followed closely for MPNST development. For most cases, treatment should include aggressive surgery with wide surgical margins combined with adjuvant radiation therapy. Chemotherapy may have a role for treatment failures.

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.

A case of neurofibrosarcoma associated with neurofibromatosis--ganglioside analysis

A patient with neurofibromatosis developed neurofibrosarcoma (NFS). The tumour was composed of spindle-shaped cells with atypical nuclei arranged in a fascicular or sheet-like fashion. The tumour cells had discontinuous basement membrane-like structures and were positively stained with the monoclonal antibody against S100 protein alpha chain. Both the primary tumour and its cultured cells contained GM3 and GD3 as major gangliosides. The ganglioside pattern of the primary tumour corresponds to that of NFS in our previous study. In the cultured NFS cells, the relative amount ratio of GM3 to GD3 is almost reversed compared to that of the primary tumour. This reversion may reflect some environmental influence on the ganglioside metabolism of NFS.

Recurrence of acoustic neurilemoma as a malignant spindle-cell neoplasm. Case report

A 75-year-old man presented with a right cerebellopontine angle tumor 11 months after complete macroscopic resection of a right acoustic neurilemoma. Histological examination of the recurrent tumor showed a malignant spindle-cell neoplasm with positive staining for S-100 protein. The patient had no stigmata of von Recklinghausen's disease. It is proposed that this recurrence represents progression from a benign to a malignant acoustic nerve-sheath tumor, an event that is extremely rare outside the clinicopathological context of neurofibromatosis.

A case of neurofibrosarcoma associated with neurofibromatosis: light microscopic, ultrastructural, immunohistochemical and biochemical investigations

A case of neurofibrosarcoma (NFS) with neurofibromatosis was studied by light microscopic, ultrastructural, immunohistochemical and biochemical methods. Histologically, spindle-shaped tumor cells with atypical hyperchromatic nuclei were arranged in a fascicular or sheet-like fashion. Electron microscopic examination revealed discontinuous basement membrane-like structures. Immunohistochemical study revealed S100 protein alpha chains in tumor cells. A biochemical analysis showed large amounts of gangliosides (sialic acid 13.5 micrograms/g wet tissue weight) in tumors. GM3 and GD3 were the major components; these results were compatible with the NFS ganglioside patterns found in our previous study. Results confirmed the diagnosis of NFS and indicate that NFS clearly has some neuroectodermal characteristics and that Schwann cells may possibly be related to its origin.

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.

Cellular junctions in a spectrum of human malignant tumors

Cellular junctions in tumors are often considered a hallmark of epithelial differentiation. However, junctions are also seen in tumors having a different differentiation. This observation prompted us to study cellular junctions in malignant nonepithelial tumors. We found a variety of cellular junctions in such tumors, although the majority were poorly formed. This observation is of importance for diagnostic purposes. We have also tried to clarify the nomenclature of cellular junctions as applied in tumor diagnosis by proposing a systematic categorization of terms in everyday use by pathologists and by referring more extensively to the term paired subplasmalemmal densities (PSD) for non-well-formed junctions.

Solitary malignant schwannoma of the pancreas: report of a case and ultrastructural examination

Primary malignant schwannoma of the pancreas is rare. The reported patient, a 40-year-old white female, presented with obstructive jaundice and a large palpable mass in the upper abdomen. A Whipple procedure was performed. Electron microscopic examination of the tumor established the Schwann cell origin of the neoplasm by demonstrating basement membranes, junctional complexes, and interdigitating cytoplasmic extensions infested with basal lamina, dense neurosecretory-like granules, and axon-like structures. The inadequacy of light microscopic examination alone for establishing the diagnosis with certainty is discussed. Review of the literature revealed only one case of a malignant schwannoma of the pancreas that was not resected. This is the first report confirmed by ultrastructural examination.

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.

Retroperitoneal schwannoma

A case of retroperitoneal benign schwannoma is presented; in addition, 133 cases of retroperitoneal schwannoma reported in Japanese literature are studied. In our series 66 per cent of the cases were found to be cystic. Therefore, the cystic change may be one of the preoperative features of schwannomas, because other types of retroperitoneal tumor do not frequently form cysts. Furthermore, the necessity of postoperative electron microscopy for accurate histologic diagnosis is discussed.

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.

Distribution of collagen type IV in soft tissue tumors. An immunohistochemical study

The distribution of collagen type IV, one of the major constituents of basement membrane, was studied immunohistologically in a series of 103 soft tissue tumors including those of peripheral nerve origin, smooth muscle origin, striated muscle origin, fibrous tissue origin, fibrohistiocytic origin, adipose tissue origin, synovial tissue origin, and blood vessel origin, paragangliomas, alveolar soft part sarcomas, granular cell tumors, and epithelioid sarcomas. Intensely positive staining for collagen type IV was observed in neurilemomas, neurofibromas, malignant schwannomas, and blood vessel tumors. Weakly to moderately positive staining was seen in leiomyomas, angiomyomas, and leiomyosarcomas. In contrast, synovial, fibroblastic and fibrohistiocytic tumors, benign or malignant, were negative. In paragangliomas, granular cell tumors, and alveolar soft part sarcomas, positive staining was evident surrounding nests or clusters of tumor cells. In all tumors, staining for collagen type IV clearly illustrated the vascular pattern.

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.

Clear cell sarcoma of the kidney: a clinicopathologic study of 21 patients with long-term follow-up evaluation

The clinical and pathologic features of 21 children with clear cell sarcoma of the kidney are presented. These cases were identified among 517 primary renal tumors collected from four pediatric institutions. Abdominal mass and hematuria were the usual presenting signs. The male to female ratio was 1.3 to 1. Although the mean age at diagnosis was 3 years, the sarcomas were diagnosed earlier in boys (2 years, 7 months) than in girls (3 years, 7 months). Tumor size and weight may have accounted for this difference, since the average tumor weights were 899 g for boys and 635 g for girls. Right kidney locations predominated (14 cases). The most common site for metastasis was the skeleton (12 patients), and the skull was almost invariably involved (10 children). Bone metastases preceded the development of metastases elsewhere in nine patients, in five of whom the involvement was polyostotic. Of the 12 patients with osseous metastases, nine died within five years of diagnosis, and one died eight years and nine months after diagnosis; the remaining two patients were successfully treated with a combination of surgery, radiotherapy, and actinomycin D, vincristine, cyclophosphamide, and Adriamycin. Eight of the nine patients with lung metastases died within five years of diagnosis. Until substantial proof is found that clear cell sarcoma of the kidney is related to nephroblastoma, its identification as a non-Wilms' sarcoma would seem to be appropriate. This tumor is not the only sarcoma of the kidney, but it appears to be the most common renal sarcoma of childhood.

Malignant epithelioid schwannoma of superficial soft tissue? A case report with immunohistology and electron microscopy

Malignant epithelioid schwannoma is a well-defined entity. However epithelioid tumours arising other than in a nerve trunk, in a benign nerve sheath tumour or in neurofibromatosis are problematical. We describe a case of a nodular tumour of the cheek which recurred twice without metastasis. Light microscopy showed an amelanotic epithelioid tumour. Immunohistology showed positive staining for vimentin and S100 protein and electron microscopy showed distinctive appearances suggestive of schwannoma. We discuss the differential diagnosis of the tumour, compare it with reported tumours resembling both melanoma and schwannoma and conclude that this may be a further example of the distinctive tumour reported as "malignant epithelioid schwannoma of superficial soft tissues'.

Microfilament-undercoated plasmalemmal infoldings in a human clear-cell sarcoma

Unusual structures often found in the cytoplasm of tumor cells in a clear-cell sarcoma appeared as multilayered, concentric, oval, spiral, parallel arrays of cisternae in various planes of section. It was demonstrated that the cisternal membrane and cavity were continuous with plasmalemmas of tumor cells and the extracellular space, respectively, suggesting that the structures were formed by the intracytoplasmic infoldings of plasmalemmas. Another characteristic found in the structures was orderly microfilaments with an average diameter of 6.5 nm which were placed between the confronting plasmalemmas in the infoldings. The filaments which underlay the infolded plasmalemmas ran parallel to each other along the cytoplasmic surfaces of plasmalemmas approximately 15 nm apart. The regularly arranged filaments were found in the infolded plasmalemmas, but not beneath any other area of plasmalemmas. The short ends of long filaments appeared to bend toward the inner surfaces of plasmalemma and to be directly connected with the surface proper. These results show that the filaments may be closely associated with the plasmalemmal infoldings and included as the same category of plasmalemmal undercoat. Additionally, the biological significance of the structures is discussed.

Clear cell sarcoma of the kidney with emphasis on ultrastructural studies

Clear cell sarcoma of the kidney (CCSK) is a malignant childhood tumor distinguished from Wilms' tumor by its gross, microscopic, and ultrastructural morphologic features and its propensity to metastasize to bone. Some clinical features of 75 cases of CCSK registered in the National Wilms' Tumor Studies I-III are presented along with the results of electron microscopic study of 12 tumors. Ultrastructural features of the tumor are compared to those of tumors of pericytes, Schwann's cells, renomedullary interstitial cells, fibroblasts, other renal tumors, and other clear cell tumors. Fine structural properties of primitive cells with variable numbers of organelles do not strongly suggest a histogenetic origin. The effect of formalin fixation on perinuclear cytoplasmic filaments and the tendency of tumor cell extensions to enfold the pale extracellular matrix explain the vacuolated appearance of some tumor cells.

Malignant soft tissue tumors of nerve sheath origin

Thirty-one patients with neurogenic sarcomas treated at Roswell Park Memorial Institute (RPMI) during a 10-year period were studied. The mean follow-up is 35.5 months. A specific nerve of origin could not be identified in 61.3% of patients. The most frequent site was the proximal lower extremity (38.7%). The only presenting symptom was enlarging mass in 67.7%. There was association with Von Recklinghausen's disease in 42% of the cases. Survival was significantly worse in tumors with Von Recklinghausen's disease (25.6%) compared to patients with solitary malignant schwannomas (50.9%). Twelve of 18 patients who had adequate surgical treatment initially remain disease-free, whereas only 2 of 11 patients referred following partial excision or recurrence remain disease-free (P less than 0.02). Eleven of 18 patients with grade I or II tumor are disease-free, whereas 2 of 10 patients with grade III tumor are disease-free (P less than 0.05). Resection of the sciatic nerve with wide excision is accompanied with a good functional result.

Diagnostic aspect of spindle-cell sarcomas by electron microscopy

Spindle-cell sarcomas in the somatic soft tissue and soft parts, including fibrosarcoma, leiomyosarcoma, malignant fibrous histiocytoma (MFH), and malignant schwannoma were examined by electron microscopy in order to delineate the most reliable cellular features for their diagnosis. Fibrosarcoma consisted largely of fibroblastic cells and leiomyosarcoma cells were packed in forming small cell groups with constant junctional complexes of nexus and zonula adherens types. MFH showed variable cellular features containing the cells with myofibroblastic and histiocytic differentiation. Malignant schwannoma was characterized by tumor cells having slender cytoplasmic processes with overlapping or interdigitation and thick basement membrane. These ultrastructural features were contributory to the differential diagnosis of the sarcomas examined.

Electron microscopy in the diagnosis of malignant schwannomas. A report of six cases

The diagnosis of malignant schwannoma may be difficult or impossible by light microscopy alone, if the neoplasm is poorly differentiated and if there is no clinical evidence for its arising from a nerve-trunk. Six cases of malignant schwannoma in which electron microscopy confirmed or established the diagnosis are reported. In four cases, the anatomic origin of the neoplasm arising from a large nerve was demonstrated at the time of operation, and in one of these the patient had von Recklinghausen's disease. In three of the four cases, as well as in the fifth case, in which the tumor was associated with an overlying malignant melanoma, the distinctive schwannoma patterns of Antoni types A and B tissue were absent. In the sixth case, there were no clinical clues as to nerve sheath origin, but both the light and electron microscopic features of the neoplasm were very characteristic of Schwann cell derivation. The most consistently present, ultrastructural features of malignant schwannoma are the spindle shape of the cells and the terminal cytoplasmic processes. If the processes show intertwining and if lateral cell borders are interdigitated, the diagnosis is more readily confirmed. Likewise, basal lamina is an important diagnostic feature but may be scant and focal in the very cellular and less differentiated tumors. Microfilaments are usually present, albeit in varying numbers, and they do not form the dense bodies seen in smooth muscle cells. Other diagnostically useful, but less consistent characteristics include microtubules, primary and secondary lysosomes, and dense-core type granules. Long-spacing collagen was present in only one case and in none of those reviewed from the literature. This is also an important finding. It is probable that most malignant nerve sheath neoplasms arise from Schwann cells, rather than from fibroblasts or perinurial cells, but electron microscopy often will be necessary to confirm this impression.