Solitary malignant peripheral nerve sheath tumor of the pancreas

Primary malignant peripheral nerve sheath tumors of the pancreas are rare. This is a report of a 72 year-old African male who presented with an 8 lb. weight loss and anorexia. A computed tomography (CT) scan revealed a 12 cm mid pancreatic mass. An 85% pancreatectomy (with splenectomy) was performed. Immunohistopathologic and ultrastructural (electron microscopy) evaluation established the schwann cell origin of this neoplasm. The clinical management and pathologic findings are discussed in this report as well as a review of the literature.

Neural spectrum: palisaded encapsulated neuroma and verocay body poor dermal schwannoma

We examined 25 palisaded encapsulated neuromas (PEN) of the skin and used peripherin antibody as an immunohistochemical label for axons. Quantitative analysis of the axon to schwann cell nuclear ratio for each PEN was determined by examining cross-sectioned neuroid fascicles. This revealed that 120 of the 253 cross-sectioned fascicles in PEN lacked axon and only 5% of the fascicles had an axon to schwann cell nuclear ratio greater than 1:2. In contrast, all fascicles in 40 dermal nerves adjacent to PENs as well as 35 traumatic neuromas in surgical scars had an axon to schwann cell nuclear ratio of at least 1:2 and the majority a ratio of 1:1 or higher. These results suggest that there is a spectrum between PENs which are axon rich to a form of schwannoma with an identical histopathology which lacks significant axonal content and that not all PENs are true neuromas.

Schwannoma of the pancreas: a report of two cases and a review of the literature

Schwannoma of the pancreas is a rare neoplasm. It generally affects older adults (average age, 60 yr). The sex incidence is equal. These tumors vary considerably in size and approximately two-thirds are partially cystic, which can cause clinical confusion with epithelial neoplasms. Histologically, they are typical schwannomas, with Antoni A and Antoni B areas, and they do not cause undue diagnostic problems once adequate tissue is examined histologically.

Extrarenal rhabdoid tumors of soft tissue: a clinicopathologic and immunohistochemical study of 18 cases

Rhabdoid tumor is a well-accepted clincopathologic entity among childhood renal neoplasms; similar tumors have been described in extrarenal locations. We present the clinicopathologic profile and the immunohistochemical features of a series of soft tissue rhabdoid tumors. Twenty-eight cases coded as extrarenal rhabdoid tumor (ERRT), RT, possible ERRT, and "large cell sarcoma" were retrieved from the Armed Forces Institute of Pathology soft tissue registry. The tumors were reclassified according to strict criteria by light microscopy, clinical information, immunohistochemistry, and, in some cases, electron microscopy. Soft tissue rhabdoid tumor (STRT) was defined as (1) a tumor composed of noncohesive single cells, clusters, or sheets of large tumor cells with abundant glassy eosinophilic cytoplasm, an eccentric vesicular nucleus, and an extremely large nucleolus; (2) positivity for vimentin and/or cytokeratin or other epithelial markers by immunostaining; and (3) exclusion of other tumor types with rhabdoid inclusions (melanoma, other sarcomas, carcinoma). Eighteen cases met our criteria for soft tissue rhabdoid tumors. The median patient age was 13 years (range, 6 months to 56 years). Ninety-four percent of STRT cases were positive for vimentin and 59% for pan-cytokeratin. Sixty-three percent and 60% were positive for CAM 5.2 and EMA, respectively. Seventy-nine percent stained for at least one epithelial marker; 76% stained for both vimentin and epithelial markers simultaneously. Forty-two percent stained for MSA, and 14% for CEA and SMA. CD99, synaptophysin, CD57 (Leu-7), NSE, and focal S100 protein were identified in 75%, 66%, 56%, 54%, and 31% of the STRT cases, respectively. All STRT cases examined were negative for HMB-45, chromogranin, BER-EP4, desmin, myoglobin, CD34, and GFAP. Follow-up examination in 61% of the STRT patients revealed that 64% of patients died of disease within a median follow-up interval of 19 months (range, 4 months to 5 years); 82% had metastases to lung, lymph nodes, or liver; 22% had local recurrences before metastasis; and 18% were alive without known disease status (median, 5.5 years). Soft tissue rhabdoid tumor is a highly aggressive sarcoma, predominantly of childhood. Besides having nearly consistent coexpression of vimentin and epithelial markers, STRTs show positivity for multiple neural/neuroectodermal markers that overlap with those of primitive neuroectodermal tumor.

Grading of subcutaneous soft tissue tumors by means of their relationship with the superficial fascia on MR imaging

OBJECTIVE

To assess the diagnostic value of the relationship between subcutaneous tumors and the superficial fascia in the characterization of soft-tissue masses.

DESIGN

MR studies of 64 soft tissue masses located in the subcutaneous space were reviewed. We established five grades of relationship between tumors and superficial fascia and analyzed the probability of the lesions in each group being malignant. Group 1 tumors did not contact the fascia; group 2 lesions contacted it slightly, with acute angles between the tumor and the fascia; group 3 lesions had wider contact with larger acute or right angles; group 4 tumors had even wider contact with obtuse angles with the fascia; and group 5 was composed of lesions that crossed the superficial fascia.

RESULTS

The probability of a subcutaneous lesion that crosses the superficial fascia being malignant was 6.88 times greater than for lesions that did not cross the fascia. For lesions forming obtuse angles with the fascia the probability of malignancy was 6.3 times greater than that of tumors that did not present this sign. All histologically verified fascial infiltrations occurred in malignant lesions of groups 4 and 5.

CONCLUSIONS

Malignant tumors of the subcutaneous compartment have a higher tendency to develop a close relationship with the fascia than benign lesions. Obtuse angles between superficial fascia and a subcutaneous mass or a lesion crossing the fascia strongly suggest malignancy.

Intraventricular perineurioma: case report

OBJECTIVE AND IMPORTANCE

Perineurioma, a rare benign nerve sheath neoplasm occurring in either an intraneural or soft tissue form, has never been reported to arise in the central nervous system.

CLINICAL PRESENTATION

We describe the clinical, radiological, and pathological features of a perineurioma arising in the choroid plexus of the third ventricle in a 65-year-old woman and causing obstructive hydrocephalus.

INTERVENTION

The lesion, apparently unassociated with a nerve, was gross totally resected by frontal craniotomy using a left-sided transcallosal approach. Short-term follow-up showed no evidence of recurrence.

CONCLUSION

Perineurioma of the variety found in soft tissue may occur in the central nervous system, wherein it shows the typical light microscopic, immunohistochemical (epithelial membrane antigen- and Collagen IV-positive, S-100 protein-negative), and ultrastructural (pinocytotic vesicles, discontinuous basement membrane) features.

Perineurial malignant peripheral nerve sheath tumor (MPNST): a clinicopathologic, immunohistochemical, and ultrastructural study of seven cases

Most malignant peripheral nerve sheath tumors (MPNST) are schwannian in nature. The pathologic features of MPNST with perineurial cell differentiation remain to be characterized. To determine the clinicopathologic, immunohistochemical, and ultrastructural characteristics of perineurial MPNST, 121 MPNST from the Mayo Clinic Tissue Registry were examined. Of these 23 spindle cell tumors with long processes disposed in whorls or storiform patterns, features typical of perineurioma, were studied. On the basis of immunohistochemistry (epithelial membrane antigen+/S-100-), 5 perineurial MPNST were identified among 23 tumors selected. These and two previously characterized perineurial MPNST are the subject of this study. None of seven tumors was associated with NF-1. Patients included five males and two females ranging in age from 11 to 83 years (mean, 45.7 years). The tumors measured 1.5 to 30 cm (mean, 9.1 cm) and arose in the extremities (two), trunk (two), face (one), mediastinum (one), and retroperitoneum (one). Only one tumor was nerve associated (phrenic nerve). All tumors were surgically removed. No encapsulation or neurofibroma components were noted. Necrosis was seen in three lesions. Four tumors were classified as high-grade malignant and three as low grade. Mitotic indices varied from 1 to 85/10 high-power fields (median, 16). Immunoreactivities included epithelial membrane antigen (100%), vimentin (100%), Leu-7 (57%), and CD34 (14%). Stains for S-100 protein, muscle markers, and cytokeratin were nonreactive. Ultrastructurally, perineurial-like cells were noted in three tumors and cells intermediate between perineurial and Schwann cells in one. Four tumors recurred and two metastasized; no deaths of disease were noted at follow-ups of 28 to 98 months (mean, 66.9). In conclusion, 4% of MPNST show perineurial cell differentiation. An NF-1 association has yet to be described. Nerve involvement is infrequent. Their immunophenotype (epithelial membrane antigen+/S-100-) frequently indicates ultrastructural perineurial differentiation. The prognosis of perineural MPNST appears to be more favorable than that of conventional MPNST.

Malignant melanoma extending along the ulnar, median, and musculocutaneous nerves: a case report

We analyzed a case of malignant melanoma that resembled malignant peripheral nerve sheath tumor with marked neurotropism. The subungual tumor in the right ring finger extended along the ulnar nerve for a distance of 30 cm, as well as along the median and musculocutaneous nerves, with lymph nodal metastases. The tumor consisted of interlacing spindle-shaped cells with large nuclei and distinct nucleolei. Immunohistochemically, the tumor cells were diffusely positive for S-100 protein. Five years after forequarter amputation, the patient is alive without disease. Malignant melanoma has the potential of invading several major peripheral nerves and must be distinguished from malignant peripheral nerve sheath tumor, which rarely metastasizes to regional lymph nodes.

Malignant peripheral nerve sheath tumor: analysis of treatment outcome

PURPOSE

To analyze the results of therapy for malignant peripheral nerve sheath tumor (MPNST) and to identify prognostic factors of survival, and of local and distant control of disease.

METHODS AND MATERIALS

From 1975 through 1993, 134 MPNSTs were diagnosed and treated at our institution. Tumor sites included extremities in 36 (27%) cases and non-extremities in 98 (73%). Median follow-up for survivors was 53 months (range: 7-280). There were 14 tumors of histologic grade I disease (10%), 43 of grade II disease (32%), 43 of grade III disease (32%), and 32 of grade IV (24%). Seventy-three patients (54%) underwent radiation therapy (RT) as part of their initial treatment of the primary tumor, including 14 (10%) who had brachytherapy and 16 (12%) who had intraoperative electron irradiation (IOERT) as part of their radiation course.

RESULTS

The 5- and 10-year survival rates were 52% and 34%, respectively. Local and distant failure rates at 5 years were both 49%. On univariate analysis, prognostic factors significantly related to survival (log-rank: p < 0.05) included tumor size, location of disease, history of neurofibromatosis type 1 (NF-1), history of prior irradiation, surgical margin status, use of IOERT or brachytherapy, disease stage, histologic grade and tumor subtype, as well as mitotic rate and the presence or absence of necrosis. On multivariate analysis, only history of prior irradiation (p = 0.023), and surgical margin status (p = 0.0044) remained significant. For local control of disease, univariate analysis showed location of disease, surgical margin status, history of NF-1, history of prior irradiation, mitotic rate, radiation dose > or = 60 Gy, and use of IOERT or brachytherapy to be significant prognostic factors. On multivariate analysis, only surgical margin status (p = 0.0024), RT dose (p = 0.021), and use of IOERT or brachytherapy (p = 0.016) remained significant. For distant control of disease, significant prognostic factors on univariate analysis included tumor size, stage, tumor grade, mitotic rate, presence or absence of necrosis, and histologic subtype. On multivariate analysis, tumor size (p = 0.0065), grade (p = 0.036), and histologic subtype (p = 0.001) remained significant. Patients with perineurial MPNSTs had a much lower rate of distant metastasis and a better overall survival as compared with other histologic subtypes.

CONCLUSION

Management of patients with MPNST involves a multi-modality approach. The goal of surgery is complete resection with negative margins. Adjuvant irradiation to doses > or = 60 Gy and the inclusion of IOERT or brachytherapy are associated with improved local control of disease.

The spectrum of neurocristic cutaneous hamartoma: clinicopathologic and immunohistochemical study of three cases

Neurocristic cutaneous hamartomas result from aberrant development of the neuromesenchyme. Thus, the elements within these tumors reflect the spectrum of differentiation that results from migration of neural crest-derived cells. We present three cases, in addition to routine hematoxylin-eosin staining, a battery of immunohistochemical staining, including S-100 protein, HMB-45, EMA, CD34, and neurofilament-protein stains, was performed on each specimen. A dermal melanocytic component was the dominant feature of two of these lesions, while neurosusenticular and neuromesenchymal components dominated in one tumor. Both tumors that developed on the scalp showed effects on the overlying epidermis and/or on adnexal development. The melanocytic component was positive for S-100 protein and HMB-45. The surrounding stroma showed tactoid bodies and increased CD34 staining. Neurocristic cutaneous hamartomas represent dysplastic development of neural crest-derived cells. Although melanocytic cells have been previously reported to be the dominant cell population, neurosusentacular and neuromesenchymal cells also may be the principal component. In cephalic areas, the neuromesenchyme may not only be an important component of the tumor, but may also effect the development of the overlying epithelium and adnexal structures. Although none of these cases presents evidence of malignant transformation, identification of these tumors could be important if malignant transformation results in the development of tumors with a distinctive biologic behavior.

Plexiform neurofibroma with and without associated malignant peripheral nerve sheath tumor: a clinicopathologic and immunohistochemical analysis of 54 cases

Plexiform neurofibroma (PNF) is an important part of the diagnostic criteria for neurofibromatosis type 1 (NF1) and is a known precursor lesion of malignant peripheral nerve sheath tumor (MPNST). We studied the clinicopathologic features of 54 cases of PNF for which the hematoxylin- and eosin-stained slides and paraffin blocks were available and adequate clinical follow-up could be obtained. In addition, in all cases, a representative section of the PNF and, when present, MPNST, was evaluated immunohistochemically with an antibody for p53 (DO7). The cohort included 28 male patients and 26 female patients, with an age range from 4 to 79 years (mean, 27 yr). Of these 54 patients, 46 (85%) met the strict diagnostic criteria for NF1. Thirty-nine patients had PNF alone; 15 patients had an MPNST arising from the PNF (PNF/MPNST). Those patients with PNF/MPNST tended to be older (38 yr vs. 22 yr) and to have larger tumors (10.5 cm mean vs. 7.4 cm mean) than those with PNF alone. In 9 patients (23%) of 39 with PNF alone, local recurrence developed, whereas in 7 patients (47%) of 15 with PNF/MPNST, recurrent MPNST developed, and metastases developed in 3 (20%) of the 15. Immunohistochemically, only 1 case (2.5%) of 39 cases of PNF alone stained for p53. On the other hand, 12 (80%) of 15 cases of PNF/MPNST showed p53 immunoreactivity in the MPNST component, 2 of which also showed staining in the PNF areas. In conclusion, we found that the vast majority of patients with PNF met the strict diagnostic criteria for NF1. The immunohistochemical detection of intranuclear p53 protein is common in the malignant areas of PNF/MPNST but is rare in the PNF regions. The rarity of p53 staining in the PNF regions precludes its use in predicting those tumors that are likely to progress to MPNST.

Histopathological and immunohistochemical studies of intracranial nervous-system tumours in four cattle

Intracranial nervous-system tumours were diagnosed in three of 1092 bovine necropsy specimens submitted to the Department of Veterinary Pathology, Obihiro University between April 1983 and March 1996. A fourth case was a referral from the Department of Veterinary Pathology, Rakuno Gakuen University. Histopathological examination revealed four types of tumour: intracranial malignant peripheral nerve sheath tumour (MPNST), choroid plexus papilloma, differentiated fibrillary astrocytoma and anaplastic (malignant) astrocytoma. Immunohistochemically, the intracranial MPNST was strongly positive for S-100 protein and vimentin, and in places weakly positive for glial fibrillary acid protein (GFAP). The choroid plexus papilloma was strongly positive for epithelial membrane antigen (EMA), keratin, S-100 protein and vimentin, and positive for GFAP in places. The cytoplasm and fibrous component in the differentiated fibrillary astrocytoma were strongly positive for S-100 protein and GFAP. The anaplastic (malignant) astrocytoma was strongly positive for vimentin, S-100 protein and keratin in the cytoplasm and fibrous processes, and weakly positive for GFAP and EMA in places. Myelin basic protein (MBP) and synaptophysin showed a weak positive reaction in the marginal areas of the tumour.

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

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

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.

Intraosseous malignant peripheral nerve sheath tumor in a patient with neurofibromatosis

Malignant peripheral nerve sheath tumors (MPNSTs) are uncommon sarcomas that almost always arise in soft tissue. They can develop in pre-existing neurofibromas or schwannomas, de novo from peripheral nerves, or following radiation therapy. Primary intraosseous MPNST is rare and has been reported most frequently in the mandible. Of the reported cases involving the long bones, none has been associated with neurofibromatosis type 1 (NF-1). We report a case of MPNST arising in the femur in a patient with NF-1.

[Malignant peripheral nerve sheath tumor. Vagus nerve sarcoma]

A young man was seen for a mass on the left side of the neck. Computed tomography revealed a round mass suggesting a lymph node metastasis with a necrotic center. Fine needle aspiration found mesenchymal cells. The tumor excised from its location on the Xth left cranial nerve was found to be a malignant peripheral nerve sheath tumor. Treatment was complemented by regional irradiation. After concluding complementary treatment in April 1996, the patient currently is disease-free. This type of soft-tissue sarcoma is reviewed. Survival depends on tumoral size and cellular differentiation.

Canine peripheral nerve sheath tumor with eosinophilic cytoplasmic globules

A 13-year-old male Shetland Sheepdog had a subcutaneous tumor in the left brachium. The tumor was removed and recurred several times at 5, 13, 16, 22, and 31 months after the initial presentation. Histologically, the removed nodules from the fourth resection were composed of neoplastic proliferation of round to fusiform cells, which possessed eosinophilic globules in their cytoplasm. The globules were periodic acid-Schiff positive and diastase resistant. Positive reactions for acid phosphatase were observed in the cytoplasm of the tumor cells. Ultrastructurally, these globules consisted of membrane-bound, dense structures containing dense granules, lucent vacuoles, and homogeneous materials. The recurrent tumors removed at the fifth resection consisted of spindle cell proliferation arranged in interlacing fascicles with wavy nuclei and containing a small number of cells with cytoplasmic globules. The tumor cells were immunoreactive to vimentin, S-100 protein, myelin basic protein, and neuron-specific enolase. The tumor was diagnosed as a peripheral nerve sheath tumor with eosinophilic cytoplasmic globules. These findings are unique for the histogenesis of granular cell tumors.

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

AIMS

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

METHODS AND RESULTS

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

CONCLUSIONS

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

Perineurioma of the finger: case report of a rare peripheral nerve sheath neoplasm of pure perineurial cell lineage

A 1.9-cm extraneural soft tissue tumor located on the palmar aspect of the index finger of a 50-year-old woman was excised. Depicting many histopathologic patterns and a full range of cellularity, the tumor was exclusively composed of epithelial membrane antigen/vimentin-positive and S-100 protein/Leu-7-negative neoplastic cells of perineurial lineage. Soft tissue (extraneural) perineurioma, a rare variant of benign peripheral nerve sheath tumor, should be included in the differential diagnosis of tumor and tumor-like conditions affecting soft parts of the hand.

Malignant peripheral nerve sheath tumors developing multifocally in the central nervous system in a patient with neurofibromatosis type 2

We describe autopsy findings of multifocal malignant peripheral nerve sheath tumors (MPNSTs) appearing in the central nervous system in a 45-year-old Japanese female with neurofibromatosis type 2. Multiple MPNSTs were detected in both III and VIII, left IV, and V cranial nerves, and a number of nerve roots of the spinal cord. Neurofibromata were on the other hand evident on some nerve roots of the spinal cord and femoral and sciatic nerves. Our results suggest that a mutation of p53 gene may have played a role in the malignant transformation of nerve tumors in this patient since p53 protein was immunohistochemically detected in MPNST cells but not in tumor cells of the neurofibromata.

Benign neural sheath tumours of major nerves: characteristics in 119 surgical cases

Peripheral benign nerve sheath tumours are infrequent tumours and affect major nerve trunks. Some authors have indicated a high and prohibitive incidence of neurological injury in resection of these lesions. The authors describe their findings in a retrospective study comprising 119 patients with spontaneous benign nerve sheath tumours of the peripheral nervous system. Seventy-three patients had a schwannoma, 41 had neurofibroma and 5 had plexiform neurofibroma; 25 of the 119 patients suffered from neurofibromatosis. All schwannomas were excised completely and the outcome of patients was 41.0% improved, 6.8% worsened, 52.0% unchanged. Twenty-eight neurofibromas were excised completely and 13 subtotally; the outcome for patients was 19.5% improved, 19.5% worsened and 61% unchanged. All plexiform neurofibromas were removed subtotally and the outcome for patients was 20% improved and 80% unchanged. The best surgical results at average follow-up of 6 years were observed in the patients with schwannoma, the worst in those with plexiform neurofibroma. Our results demonstrated that it is often possible to remove schwannomas as well as neurofibromas with an acceptable risk of injury to the nerve.

Neoplasms with neural differentiation: a review. Part II: Malignant neoplasms

Malignant peripheral nerve sheath tumors (MPNSTs) encompass a wide and unusual group of neoplasms with features of neural differentiation. They most commonly present as spindle cell neoplasms and it can be difficult to differentiate them from other spindle cell neoplasms such as leiomyosarcomas, fibrosarcomas and synovial sarcomas. Strict criteria need to be applied in order to make the diagnosis of MPNSTs. Helpful features include contiguity with a nerve or an association with von Recklinghausen disease. The use of immunohistochemical stains may also help to confirm the diagnosis. Markers such as S-100 protein, neurofilament, epithelial membrane antigen and Leu-7 (CD57) are frequently used to assess neural differentiation in these neoplasms. In addition to the spindle cell pattern, MPNSTs may also display an epithelioid pattern. Rarely, other elements may be seen including glands in the so-called glandular MPNST or muscle in triton tumors. In more unusual cases cartilage, adipose tissue and even bone are present. Also included in the group of MPNSTs are the peripheral neuroepithelial tumor, neurotropic or desmoplastic melanomas and malignant granular cell tumors. MPNSTs are highly aggressive tumors and should be treated accordingly.