Extremity malignant peripheral nerve sheath tumors (neurogenic sarcomas): a 10-year experience

Histology-Tailored Approach to Soft Tissue Sarcoma

Soft tissue sarcomas are a diverse and heterogeneous group of cancers of mesenchymal origin. Each histological type of soft tissue sarcoma has unique clinical particularities, which makes them challenging to diagnose and treat. Multidisciplinary management of these rare diseases is thus key for improved survival. The role of surgery has been well established, and it represents the cornerstone curative treatment for soft tissue sarcomas. To date, local recurrence is the leading cause of death in low-grade sarcomas located at critical sites, and distant metastasis in high-grade sarcomas, regardless of the site of origin. Management must be tailored to each individual histologic type. We describe the most common types of extremity, trunk, abdominal, and retroperitoneal soft tissue sarcoma along with characteristics to consider for optimized management.

Malignant Peripheral Nerve Sheath Tumors: Latest Concepts in Disease Pathogenesis and Clinical Management

Malignant peripheral nerve sheath tumor (MPNST) is an aggressive soft tissue sarcoma with limited therapeutic options and a poor prognosis. Although neurofibromatosis type 1 (NF1) and radiation exposure have been identified as risk factors for MPNST, the genetic and molecular mechanisms underlying MPNST pathogenesis have only lately been roughly elucidated. Plexiform neurofibroma (PN) and atypical neurofibromatous neoplasm of unknown biological potential (ANNUBP) are novel concepts of MPNST precancerous lesions, which revealed sequential mutations in MPNST development. This review summarized the current understanding of MPNST and the latest consensus from its diagnosis to treatment, with highlights on molecular biomarkers and targeted therapies. Additionally, we discussed the current challenges and prospects for MPNST management.

Management of pelvic sarcoma

Pelvic sarcomas are a rare and heterogenous group of tumors divided into two groups: soft tissue sarcomas and bone sarcomas. Soft tissue sarcomas of the pelvis include most commonly liposarcoma, leiomyosarcoma, gastrointestinal stromal tumors, malignant peripheral nerve sheath tumors, and solitary fibrous tumors. Bone sarcomas of the pelvis most commonly include osteosarcoma and chondrosarcoma. Multidisciplinary treatment at a center experienced in the treatment of sarcoma is essential. Management is dictated by histologic type and grade. Surgical resection with wide margins is the cornerstone of treatment for pelvic sarcomas, although this is often challenging due to anatomic constraints of the pelvis. Multimodal treatment is critical due to the high risk of local recurrence in the pelvis.

Epidemiology, Characteristic, and Prognostic Factors of Primary Sporadic Intradural Malignant Peripheral Nerve Sheath Tumor in the Spinal Canal: A Systematic Literature Review

Purpose

Primary sporadic intradural malignant peripheral nerve sheath tumor (MPNST) in the spinal canal is a type of rare neoplasm with challenging diagnosis and therapy. The overall prognosis of this tumor is markedly different from that of the usual spinal intradural tumors. The purpose of this systematic review is to reduce the misdiagnosis and enhance the prognosis of the disease by reviewing the literature.

Methods

PubMed, Medline, and Embase databases were searched for articles in English language published from 1980 to May 2021, yielding 500 potentially relevant articles. The keywords were as follows: “spinal”, “malignant peripheral nerve sheath tumor”, “neurosarcoma”, “malignant schwannoma”, and “malignant neurofibroma”. Thirteen papers met the eligibility criteria, including 55 cases with spinal intradural primary sporadic MPNSTs, which were confirmed by post-operation pathology. We further analyzed the clinical manifestations, radiological manifestations, pathological features, comprehensive treatment strategies, and prognosis.

Results

Fifty-five spinal intradural primary sporadic MPNSTs from 30 (54.5%) male and 25 (45.5%) female patients with an average age at diagnosis of 40 years (range, 3–70 years) were included in the study. The most common clinical manifestations were local or radicular pain and motor disturbance. All tumors had significant enhancement and heterogeneous enhancement was more common. Out of 18 lesions, 14 were diagnosed as high grade and the remaining 4 were diagnosed as low grade. The ki-67 labeling index ranged from 5% to 60%. The median recurrence and survival time were 36 and 72 months, respectively. The log-rank tests indicated that significant predictors of OS were patient age (≤30 vs. >30 years) at the time of diagnosis and the presence of metastatic disease, and similar analyses for RFS demonstrated that the presence of metastatic disease was the only significant predictor (60 vs. 10 months). The multivariate Cox proportional hazards regression analysis revealed that absence of metastasis was an independent factor for predicting a favorable prognosis.

Conclusions

Spinal intradural primary sporadic MPNSTs are challenging malignant tumors without a systematic treatment plan. The factors affecting its prognosis are not clear. Even after surgical treatment and adjuvant treatment, the recurrence rate and mortality rate are still high. Clinicians should be alert to the possibility of this disease and achieve early detection and treatment.

Recurrent malignant peripheral nerve sheath tumor presenting as an asymptomatic intravenous thrombus extending to the heart: a case report

Background

Malignant peripheral nerve sheath tumor (MPNST) is a rare soft tissue sarcoma mainly treated via surgical resection. Herein, we report a case of MPNST wherein a massive tumor thrombus extended to the major veins and heart.

Case presentation

A 39-year-old female with a history of neurofibromatosis type 1 developed MPNST from the right radial nerve. In addition to adjuvant chemotherapy, she underwent wide tumor resection and concomitant radial nerve resection, followed by postoperative radiotherapy. Histological evaluation revealed marked venous invasion. The 2-year follow-up CT revealed an asymptomatic recurrent tumor thrombus extending from the right subclavian vein to the heart. An urgent life-saving operation was performed to ligate the base of the right subclavian vein and remove the entire intravenous thrombus that extended to the right ventricle. The remaining tumor in the right subclavian vein increased in size 3 months after thrombectomy. After confirming the absence of any metastatic lesions, the patient underwent extended forequarter amputation to achieve surgical remission. One year later, a new metastasis to the right diaphragm was safely resected. The patient remains alive without any evidence of disease 2 years after the extended forequarter amputation.

Conclusions

In cases of a previous history of microscopic venous invasion, recurrence can occur as a massive tumor thrombus that extends to the great vessels.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-021-02473-2.

Systemic Options for Malignant Peripheral Nerve Sheath Tumors

OPINION STATEMENT

Malignant peripheral nerve sheath tumors (MPNSTs) are rare mesenchymal neoplasms that represent a profound therapeutic challenge due to their high proclivity for recurrence and metastasis and relatively poor response to systemic therapy regimens. While our understanding of the pathophysiology of MPNST is growing, including loss of the tumor suppressor gene neurofibromin and subsequent activation of the Ras pathway, targeted therapy to modify the poor prognosis seen in MPNST patients has thus far been without success. Correspondingly, MPNST patients are treated as per soft tissue sarcoma treatment algorithms with anthracycline-based therapy as the front-line therapy of choice for patients with unresectable, locally advanced, or metastatic MPNST. Beyond first-line anthracycline-based therapy, other standard cytotoxic chemotherapy agents used in advanced MPNST include the alkylating agent ifosfamide and the topoisomerase II inhibitor etoposide. Notably, soft tissue sarcoma regimens are used in MPNST despite distinct systemic therapy sensitivity and prognosis. This is particularly notable for neurofibromatosis type 1 (NF1)-associated MPNST, which is associated with poorer response to systemic therapy and prognosis than sporadic MPNST. As such, NF1-associated MPNST is a particular area in need of novel therapeutic strategies. Given the lack of benefit in the targeting of unique aspects of MPNST disease biology thus far, pre-clinical studies to identify novel rational therapies are critical to inform future clinical trials.

Prognosis and risk factors for malignant peripheral nerve sheath tumor: a systematic review and meta-analysis

Background

No available meta-analysis was printed to systematically introduce the MPNST clinic outcome and risk factors based on largely pooled data. This systematic review and meta-analysis aimed to investigate 5-year OS rate, 5-year EFS rate, and LR rate for MPNST, and to assess potential risk factors for prognosis.

Methods

Electronic articles published between January 1, 1966 and February 29, 2020 were searched and critically evaluated. The authors independently reviewed the abstracts and extracted data for 5-year OS rate, 5-year EFS rate, LR rate, and potential risk factors for prognosis.

Results

Twenty-eight literatures were finally included for meta-analysis. The pooled 5-year OS rate, 5-year EFS rate, and LR rate were 49%, 37%, and 38%, respectively. The significant prognostic factors for survival were NF1 status, tumor size, depth, location, malignant grade, margin status, chemotherapy, and radiotherapy. Age and sex were not associated with survival.

Conclusion

Survival and local recurrence of MPNST are poor. Worse prognosis is mainly associated with NF 1, large size, deep to fascia, high grade, metastases, and location (trunk and head and neck). Complete resection with adequate surgical margins is the mainstay protective factor of MPNST patients, following necessary adjuvant therapies.

Malignant Peripheral Nerve Sheath Tumor of the Cervical Spine Treated with Surgical Resection Followed by X-ray Radiotherapy or Carbon Ion Radiotherapy: A Report of Three Cases

Introduction

Spinal malignant peripheral nerve sheath tumors (MPNSTs) are extremely rare. Because of vital surroundings, en bloc resection can be difficult in MPNSTs of the cervical spine. Herein, we report three cases of MPNST followed by radiotherapy or carbon ion radiotherapy (CIRT) after surgery.

Technical Note

In case 1, the patient underwent subtotal resection from both a posterior and anterior approach following by adjuvant X-ray radiotherapy. The patient died 13 years after surgery due to liver cancer unrelated to MPNST. In case 2, recurrence spread to the spinal canal in 10 months after primary CIRT. The patient underwent resection of the spinal canal lesion with the residual lesion treated by additional CIRT. Recurrence could be controlled for at least 1 year. In case 3, the patient underwent partial resection for the spinal canal lesion with the residual lesion treated by CIRT. Intradural and extradural recurrences from outside of the CIRT field were observed at 3 years after surgery.

Conclusions

Complete resection and adjuvant X-ray radiotherapy would be an effective treatment for MPNST of the cervical spine, even if en bloc resection with a wide margin is impossible. CIRT for the residual tumor after incomplete resection may have the potential to be an additional treatment option; however, further investigation is warranted.

Clinical presentation and long-term outcome of primary spinal intradural malignant peripheral nerve sheath tumors

OBJECTIVE

Primary spinal intradural malignant peripheral nerve sheath tumors (MPNSTs) are exceedingly rare, and there is limited published information regarding these lesions. The purpose of this study was to analyze the clinical course, treatment, and outcome of primary spinal intradural MPNSTs.

PATIENTS AND METHODS

A retrospective study was performed on 8 patients with primary spinal intradural MPNSTs who were surgically treated and pathologically confirmed in our institution between 2007 and 2018.

RESULTS

There were 3 females and 5 males, with a median age of 46.5 years (range, 21-68 years). Limb weakness was the most common clinical symptom (5/8, 62.5%). The radiological diagnosis was meningioma or schwannoma in most patients (7/8, 87.5%). Malignancies were graded high in 5 cases (62.5%) and low in 3 cases (37.5%). Gross total resection (GTR) was performed in 5 cases, while subtotal resection (STR) was achieved in 3 cases. The mean follow-up period was 48.9 months (range, 10-160 months). During follow-up, local recurrence occurred in 6/8 cases (75.0%) and distant metastasis occurred in 2/8 cases (25.0%). The median survival time (MST) of these 8 patients was 21.0 months. The overall 1-year, 2-year, and 5-year survival rates were 87.5% (7/8), 50.0% (4/8), and 25.0% (2/8), respectively.

CONCLUSIONS

Primary spinal intradural MPNST is a challenging clinical entity given its high local relapse rate. Primary spinal intradural MPNSTs radiologically present themselves heterogeneous and thus difficult to distinguish from schwannomas or meningiomas. Surgical resection, especially GTR, is the preferential treatment for primary spinal intradural MPNSTs.

Treatment and survival differences across tumor sites in malignant peripheral nerve sheath tumors: a SEER database analysis and review of the literature

Background

Currently, literature is scarce on differences across all possible tumor sites in malignant peripheral nerve sheath tumors (MPNSTs). To determine differences in treatment and survival across tumor sites and assess possible predictors for survival, we used the Surveillance, Epidemiology, and End Results (SEER) database.

Methods

MPNST cases were obtained from the SEER database. Tumor sites were recoded into: intracranial, spinal, head and neck (H&N), limbs, core (thorax/abdomen/pelvis), and unknown site of origin. Patient and tumor characteristics, treatment modalities, and survival were extracted. Overall survival (OS) was assessed using univariable and multivariable Cox regression hazard models. Kaplan-Meier survival curves were constructed per tumor site for OS and disease-specific survival (DSS).

Results

A total of 3267 MPNST patients were registered from 1973 to 2013; 167 intracranial (5.1%), 119 spinal (3.6%), 449 H&N (13.7%), 1022 limb (31.3%), 1307 core (40.0%), and 203 unknown (6.2%). The largest tumors were found in core sites (80.0 mm, interquartile range [IQR]: 60.0-115.0 mm) and the smallest were intracranial (37.4 mm, IQR: 17.3-43.5 mm). Intracranial tumors were least frequently resected (58.1%), whereas spinal tumors were most often resected (83.0%). Radiation was administered in 35.5% to 41.8%. Independent factors associated with decreased survival were: older age, male sex, black race, no surgery, partial resection, large tumor size, high tumor grade, H&N site, and core site (all P < .05). Intracranial and pediatric tumors show superior survival (both P < .05). Intracranial tumors show superior OS and DSS curves, whereas core tumors have the worst (P < .001).

Conclusion

Superior survival is seen in intracranial and pediatric MPNSTs. Core and H&N tumors have a worse prognosis.

Rectal Neurogenic Sarcoma: Case Report and Review of the Literature

A neurogenic sarcoma without NF-1 was discovered in a 73-year-old woman in the anorectal region, an unusual site for these tumors. The tumor was of high-grade malignancy and deeply located with mesorectal infiltration; it did not originate from a major nerve. We presume an origin from less differentiated neural crest cells and present a review of the literature on the best treatment for these neoplasms.

Salvage rates and prognostic factors after relapse in children and adolescents with malignant peripheral nerve sheath tumors

BACKGROUND

Malignant peripheral nerve sheath tumor (MPNST) is one of the most common nonrhabdomyosarcoma soft tissue sarcomas encountered in pediatric age, and it is generally characterized by poor outcome, particularly for relapsing patients.

MATERIALS AND METHODS

This study considered 73 patients <21 years of age with relapsing MPNST observed among 120 patients enrolled in Italian pediatric protocols from 1979 to 2004. With the aim of possibly establishing a risk-adapted stratification, patients' outcome was examined using univariate and multivariate analysis based on clinical features at onset, first-line treatments, clinical findings at the time of first relapse, and second-line treatments.

RESULTS

The time to relapse ranged from 1 to 204 months after first diagnosis (median 7 months). The first relapse event was mainly local. At the time of our analysis, nine patients were alive in remission. The median overall survival after first relapse was 11 months, and the survival rates were 39.2% at 1 year and 15.8% at 5 years. The factors revealing the greatest impact on prognosis were as follows: initial tumor invasiveness, time of relapse, and achievement of a secondary complete remission (which was related to the feasibility of radical surgery).

CONCLUSIONS

Our study confirmed the unsatisfactory prognosis for pediatric patients with relapsing MPNST and pointed to a risk-adapted stratification model for the purposes of deciding second-line treatments. For the time being, an aggressive surgical approach seems to be the only effective salvage treatment and should be recommended. New therapeutic approaches are under evaluation with a view to improving current outcomes.

MEK inhibitors enhance therapeutic response towards ATRA in NF1 associated malignant peripheral nerve sheath tumors (MPNST) in-vitro

OBJECTIVE

Neurofibromatosis type 1 (NF1) is a hereditary tumor syndrome characterized by an increased risk of malignant peripheral nerve sheath tumors (MPNST). Chemotherapy of MPNST is still insufficient. In this study, we investigated whether human tumor Schwann cells derived from NF1 associated MPNST respond to all-trans retinoic acid (ATRA). We analyzed effects of ATRA and MEK inhibitor (MEKi) combination therapy.

METHODS

MPNST cell lines S462, T265, NSF1 were treated with ATRA and MEKi U0126 and PD0325901. We assessed cell viability, proliferation, migration, apoptosis and differentiation as well as mRNA expression of RAR and RXR subtypes and ATRA target genes such as CRABP2, CYP26A1, RARB and PDK1. We also analyzed CRABP2 methylation in cell lines and performed immunohistochemistry of human MPNST specimens.

RESULTS

ATRA therapy reduced viability and proliferation in S462 and T265 cells, accompanied by differentiation, apoptosis and reduced migration. NSF1 cells which lacked RXRG expression did not respond to ATRA. We furthermore demonstrated that ATRA signaling was functional for common targets, and that mRNA expression of CRABP2 and its targets was raised by ATRA therapy, whereas alternative pathways via FABP5 were not induced. Finally, combination of ATRA and MEKi demonstrated additively reduced viability of T265 and S462 cells.

CONCLUSIONS

We observed therapeutic effects in two of three MPNST cell lines pronounced by combination therapy. These data point to a potentially successful treatment of MPNST by combined application of ATRA and MEK inhibitors such as U0126 or PD0325901.

Malignant peripheral nerve sheath tumors of the spine: results of surgical management from a multicenter study

OBJECTIVE

Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft-tissue sarcomas. Resection is the mainstay of treatment and the most important prognostic factor. However, complete resection of spinal MPNSTs with tumor-free margins is challenging due to the likelihood of residual tumor cells. The objective of this study was to describe whether the type of Enneking resection in the management of spinal MPNSTs had an effect on local recurrence and survival.

METHODS

The AOSpine Knowledge Forum Tumor developed a multicenter database that includes demographic, diagnostic, therapeutic, local recurrence, and survival data on patients with primary spinal column tumors. Patients who had undergone surgery for a primary spinal MPNST were included and were analyzed in 2 groups: 1) those undergoing Enneking appropriate (EA) resections and 2) those undergoing Enneking inappropriate (EI) resections. EA surgery was performed if there was histopathological evidence of an intact tumor pseudocapsule and at least a marginal resection on a vital structure. EI surgery was performed if there was an intentional or inadvertent transgression of the margin.

RESULTS

Between 1993 and 2012, 29 primary spine MPNSTs were identified in 12 (41%) females and 17 (59%) males with a mean age at diagnosis of 40 ± 17 years (range 5–74 years). The median patient follow-up was 1.3 years (range 42 days to 11.2 years). In total, 14 (48%) patients died and 14 (48%) patients suffered a local recurrence, 10 (71%) of whom died. Within 2 years after surgery, the median survival and local recurrence were not achieved. Data about Enneking appropriateness of surgery were available for 27 patients; 9 (33%) underwent an EA procedure and 18 (67%) underwent an EI procedure. Enneking appropriateness did not have a significant influence on local recurrence or survival. Twenty-two patients underwent adjuvant treatment with combined chemo- and radiotherapy (n = 7), chemotherapy alone (n = 3), or radiotherapy alone (n = 12). Adjuvant therapy had no significant influence on recurrence or survival.

CONCLUSIONS

The rates of recurrence and survival were similar for spinal MPNSTs regardless of whether patients had an EA or EI resection or received adjuvant therapy. Other factors such as variability of pathologist interpretation, PET CT correlation, or neurofibromatosis Type 1 status may play a role in patient outcome. Nonetheless, MPNSTs should still be treated as sarcomas until further evidence is known. The authors recommend an individualized approach with careful multidisciplinary decision making, and the patient should be informed about the morbidity of en bloc surgery when considering MPNST resection.

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.

Clinical analysis of spinal stereotactic radiosurgery in the treatment of neurogenic tumors

OBJECT

In this study the authors sought to evaluate clinical outcomes after using stereotactic radiosurgery (SRS) to treat benign and malignant spinal neurogenic tumors.

METHODS

The authors reviewed a total of 66 procedures of spinal SRS performed between 2001 and 2013 for 110 tumors in 58 patients with spinal neurogenic tumors, which included schwannomas, neurofibromas, and malignant peripheral nerve sheath tumors (MPNSTs). The clinical and radiological findings were evaluated in patients with benign neurogenic tumors. For the 4 patients with MPNSTs, the authors reported overall survival and results of additional immunohistochemical staining to predict the survival difference among the patients.

RESULTS

Of the 92 benign neurogenic tumors, 65 tumors that were serially followed up using MRI after SRS showed significant change in mean tumor volume, from a mean of 12.0 ± 2.6 cm3 pre-SRS to 10.8 ± 2.5 cm3 post-SRS (p = 0.027), over an average of 44 months. The local control rate of benign neurogenic tumors was 95.4%. The 34 patients who presented with clinical symptoms of pain showed a significant symptomatic improvement. The initial mean visual analog scale (VAS) score was 6.0 and decreased dramatically to 1.0 after SRS during an average follow-up period of 10.9 months (median of 8.1 months). Although the proportions of transient swelling and loss of intramural enhancement were significantly different among the groups, there was no statistically significant correlation between those 2 factors and local tumor control (p = 0.253 and 0.067, respectively; Fisher’s exact text). Cross-table analysis also indicated that there was no statistically significant relationship between groups with loss of intramural enhancement and transient swelling. The median survival of neurofibromatosis Type 1 (NF1)-related and sporadic MPNSTs was 1.13 and 5.8 years, respectively. Immunohistochemical results showed that S100 was expressed in a sporadic MPNST or neurofibroma, whereas topoisomerase-IIa was expressed in NF1-related MPNSTs.

CONCLUSIONS

SRS is an effective treatment modality for benign neurogenic tumors, while MPNSTs showed heterogeneity in their responses to SRS.

Gender dimorphism and age of onset in malignant peripheral nerve sheath tumor preclinical models and human patients

Background

Gender-based differences in disease onset in murine models of malignant peripheral nerve sheath tumor (MPNST) and in patients with Neurofibromatosis type-1-(NF-1)-associated or spontaneous MPNST has not been well studied.

Methods

Forty-three mGFAP-Cre+;Pten^loxp/+;LSL-K-ras^G12D/+ mice were observed for tumor development and evaluated for gender disparity in age of MPNST onset. Patient data from the prospectively collected UCLA sarcoma database (1974–2011, n = 113 MPNST patients) and 39 published studies on MPNST patients (n = 916) were analyzed for age of onset differences between sexes and between NF-1 and spontaneous MPNST patients.

Results

Our murine model showed gender-based differences in MPNST onset, with males developing MPNST significantly earlier than females (142 vs. 162 days, p = 0.015). In the UCLA patient population, males also developed MPNST earlier than females (median age 35 vs. 39.5 years, p = 0.048). Patients with NF-1-associated MPNST had significantly earlier age of onset compared to spontaneous MPNST (median age 33 vs. 39 years, p = 0.007). However, expanded analysis of 916 published MPNST cases revealed no significant age difference in MPNST onset between males and females. Similar to the UCLA dataset, patients with NF-1 developed MPNST at a significantly younger age than spontaneous MPNST patients (p < 0.0001, median age 28 vs. 41 years) and this disparity was maintained across North American, European, and Asian populations.

Conclusions

Although our preclinical model and single-institution patient cohort show gender dimorphism in MPNST onset, no significant gender disparity was detected in the larger MPNST patient meta-dataset. NF-1 patients develop MPNST 13 years earlier than patients with spontaneous MPNST, with little geographical variance.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-827) contains supplementary material, which is available to authorized users.

Radiation-induced intradural malignant peripheral nerve sheath tumor of the cauda equina with diffuse leptomeningeal metastasis

Malignant peripheral nerve sheath tumors (MPNSTs) are rare, affecting only a small portion of the general population. In many cases, MPNSTs occur in association with neurofibromatosis Type 1 and at times arise secondary to previous radiation therapy (RT). These tumors can be found essentially anywhere a peripheral nerve is present, but they rarely originate primarily from the spinal nerve or cauda equina and cause leptomeningeal spread. This report describes the treatment course of a 43-year-old man with a history of testicular seminoma treated with RT a decade before, who was found to have a large sacral MPNST. The patient underwent complete sacrectomy for gross-total resection. Despite this effort, he was eventually found to have metastatic lesions throughout the spine and brain, ultimately resulting in acute hydrocephalus and death. Biopsy results of these metastatic lesions proved to be characteristic of his original MPNST. The literature is also reviewed and the diagnostic modalities, management strategies, and prognosis of MPNST are discussed.

Malignant peripheral nerve sheath tumors in children with neurofibromatosis type 1

Purpose. Malignant peripheral nerve sheath tumors (MPNSTs) are rare in children and account for approximately 5–10% of all soft tissue sarcomas in adults. MPNSTs may occur independently but individuals with neurofibromatosis type 1 (NF1) have a significantly increased risk. Our aim is to present patients with MPNST treated in our department. Cases and Results. In this report we present 4 cases of MPNSTs (3 females: 13, 12, and 13 years old and 1 male: 10 years old) arising in patients with NF1. All of them presented with an enlarging mass and pain at diagnosis. Tumor was located in the buttock, the spinal cord, the trunk, and the left leg proximal to the heel. Wide excision of the tumor and radiotherapy were applied to all and adjuvant chemotherapy was given to three of them after the disease was progressed. All four died 32, 18, 10, and 22 months after diagnosis with progressive disease locally and pulmonary metastases in two of them. Conclusions. In conclusion, MPNSTs arising in patients with NF1 are high grade sarcomas with short survival. Individuals with NF1 should be followed closely in order to identify early the development of MPNSTs. Aggressive surgery and complete excision significantly improves disease-free survival. The usefulness of radiation therapy in MPNSTs is not determined although all patients will receive radiation therapy at some stage of the disease. The role of chemotherapy is unclear.

Malignant Peripheral Nerve Sheath Tumors Masking as Ewing Sarcoma/Primitive Neuroectodermal Tumors

Malignant peripheral nerve tumors, a small subset of soft tissue sarcomas, provide a unique diagnostic challenge. Although they may arise from peripheral nerves or from cells associated with nerve sheaths, malignant peripheral nerve tumors often present with diverse immunohistochemical features similar to those of other tumors. These features make MPNSTs difficult to diagnose and classify. We present a case of a 26-year-old female presenting with a rapidly growing soft tissue mass. The mass was excised and immunohistological staining suggested a Ewing’s sarcoma/Primitive neuroectodermal tumor. Confirmational studies did not confirm this diagnosis and upon further review, the diagnosis was changed to a malignant peripheral nerve sheath tumor. We reviewed this case in the setting of the reported literature concerning MPNSTs with focus on the epidemiologic, diagnostic, and immunohistologic features that distinguish this tumor from other similar malignancies.

Concurrence of malignant peripheral nerve sheath tumor at the site of complex regional pain syndrome type 1 - a case report -

Malignant peripheral nerve sheath tumors (MPNSTs) are very rare sarcomas derived from various cells in the peripheral nerve sheath. Malignant peripheral nerve sheath tumors have a known association with neurofibromatosis type 1. Diagnosis of MPNSTs is difficult in patients with chronic pain, when MPNST occurs at an overlapping area of chronic pain. Therefore, the diagnosis can be missed unless clinicians pay attention to the possibility of this disease. Here in, we report a case of concurrent malignant peripheral nerve sheath tumor with complex regional pain syndrome type 1. A 44-year female patient, who was diagnosed with complex regional pain syndrome (CRPS) type 1 in her left ankle, visited our clinic because of aggravated pain. The cause of the aggravated pain was revealed as concurrent MPNST in the left common peroneal nerve territory, which overlapped the site of pain from CRPS.

Malignant peripheral nerve sheath tumours of the spine: clinical manifestations, classification, treatment, and prognostic factors

BACKGROUND AND OBJECTIVES

To summarise our experience treating patients with spinal malignant peripheral nerve sheath tumours (MPNSTs).

METHODS

We retrospectively reviewed the records of patients diagnosed with spinal MPNSTs who received surgical treatment from January 1998 to December 2009.

RESULTS

Postoperative follow-up data were available for 14/16 patients with spinal MPNSTs (7 men, 7 women; median age = 44 years [range: 23-68 years]). Eight of 14 (57.1%) patients had primary and 6/14 (42.9%) recurrent MPNSTs. A total of 12/14 (85.7%) patients underwent total tumour resection, whereas 2/14 (14.3%) patients underwent subtotal tumour resection. Malignancies were graded low in 4 (28.6%) and high in 10 (71.1%) cases. A total of 12/14 (85.7%) patients experienced tumour recurrence and 10/14 (71.4%) patients died during the course of follow-up. The 0.5- 1-, 3-, and 5-year survival rates were 64.3, 48.2, 32.1, and 21.4%, respectively. Overall survival was significantly associated with tumour malignant degree (P = 0.012).

CONCLUSION

Diagnosis of spinal MPNSTs should be made with reference to clinical, radiological, and pathological findings. Surgical resection is the best available option for treating spinal MPNST; however, postoperative prognosis is poor.

Early outcomes for malignant peripheral nerve sheath tumor treated with chemotherapy

OBJECTIVES

Malignant peripheral nerve sheath tumors (MPNST) are rare soft-tissue sarcomas with a tendency for recurrence and metastasis. Treatment using chemotherapy is controversial, but benefit with some agents has been described. This study aimed to analyze early survival outcomes using doxorubicin and ifosfamide chemotherapy for MPNST.

METHODS

Pathology records at our musculoskeletal tumor center were searched for patients with a new diagnosis of MPNST between 2003 and 2008. Treatment involved surgical resection, radiation, and chemotherapy with doxorubicin and ifosfamide. Ten patients met inclusion criteria, with mean age 40 years (range, 20-70). Four patients had metastatic disease on presentation. Four patients had neurofibromatosis type I (NF1).

RESULTS

Of 6 patients with nonmetastatic disease on presentation, 5 had no evidence of disease post-treatment. The sixth had positive margins after surgery and initially received no further treatment due to noncompliance. Three from this subgroup developed local recurrence, but none developed distant metastases and 1 died of disease at last follow-up. One- and 2-year disease-free survival (DFS) for this subgroup was 80% and 60%, respectively. One- and 2-year overall survival (OS) for the subgroup was 100%. Of 4 patients with metastatic disease on presentation, 2 had no evidence of disease post-treatment. One of these 2 developed local recurrence, but none from the subgroup developed new metastatic disease. Two of these 4 died of disease at last follow-up. One- and 2-year DFS for this subgroup was 100% and 50%, respectively. One- and 2-year OS was 75% and 50%, respectively. Two of the 4 patients presenting with metastatic disease had NF1. All 3 local recurrences and 2 of the 3 deaths in this study occurred in NF1 patients.

CONCLUSIONS

For all patients, when combined with surgery and radiation, chemotherapy using doxorubicin and ifosfamide yielded 57% DFS and 80% OS at 2 years. NF1 patients appeared to have worse outcomes, with a statistically significantly lower DFS than non-NF1 patients. Limitations of this study include a small sample size, retrospective design, and use of different chemotherapy regimens.

[Malignant peripheral nerve sheath tumors: A case report]

Malignant peripheral nerve sheath tumors comprehend a rare group of soft tissue sarcomas that tend to occur in patients with neurofibromatosis type 1 or several years after radiotherapy treatments. Its thoracic localization is a very unusual entity. The typical symptoms are due to nerve roots compression which can persist for several months or years before diagnosis. Due to very few patients with this type of tumor its therapeutic approach is still a matter of permanent debate, being surgery the main treatment. This tumor has a bad prognosis because of high local recurrence and metastasis. The clinical case we describe serves as a glimpse for discussion.

Factors of influence upon overall survival in the treatment of intracranial MPNSTs. Review of the literature and report of a case

BACKGROUND

Intracranial malignant peripheral nerve sheath tumors are rare entities that carry a poor prognosis. To date, there are no established therapeutic strategies for these tumors.

METHODS

We review the present treatment modalities and present the current therapeutic dilemmas. We perform a statistical analysis to evaluate the prognostic factors for Overall Survival of these patients. Additionally, we present our experience with a 64-year-old man with a MPNST of the left cerebellopontine angle.

RESULTS

To our best knowledge, forty three patients with intracranial MPNSTs, including our case, have been published in the international literature. Our analysis showed gross total resection, radiotherapy and female gender to be beneficial prognostic factors of survival in the univariate analysis. Gross total resection was recognized as the only independent predictor of prolonged Overall Survival. In our case, we performed a gross total resection followed for the first time by stereotactically guided radiotherapy.

CONCLUSION

Considering the results of the statistical analysis and the known advantages of the stereotaxy, we suggest aggressive surgery followed by stereotactically guided radiotherapy as therapy of choice.

Quantitative F18-fluorodeoxyglucose positron emission tomography accurately characterizes peripheral nerve sheath tumors as malignant or benign

BACKGROUND

Correct pretreatment classification is critical for optimizing diagnosis and treatment of patients with peripheral nerve sheath tumors (PNSTs). The aim of this study was to evaluate whether F18-fluorodeoxyglucose positron emission tomography (FDG PET) can differentiate malignant (MPNST) from benign PNSTs.

METHODS

Thirty-four adult patients presenting with PNST who underwent a presurgical FDG PET/computed tomography (CT) scan between February 2005 and November 2008 were included in the study. Tumors were characterized histologically, by FDG maximum standardized uptake value (SUV(max) [g/mL]), and by CT size (tumor maximal diameter [cm]). The accuracy of FDG PET for differentiating MPNSTs from benign PNSTs (neurofibroma and schwannoma) was evaluated by receiver operating characteristic (ROC) curve analysis.

RESULTS

SUV(max) was measured in 34 patients with 40 tumors (MPNSTs: n = 17; neurofibromas: n = 9; schwannomas: n = 14). SUV(max) was significantly higher in MPNST compared with benign PNST (12.0 +/- 7.1 vs 3.4 +/- 1.8; P < .001). An SUV(max) cutoff point of > or =6.1 separated MPNSTs from BPSNTs with a sensitivity of 94% and a specificity of 91% (P < .001). By ROC curve analysis, SUV(max) reliably differentiated between benign and malignant PNSTs (area under the ROC curve of 0.97). Interestingly, the difference between MPNSTs and schwannomas was less prominent than that between MPNSTs and neurofibromas.

CONCLUSIONS

Quantitative FDG PET imaging distinguished between MPNSTs and neurofibromas with high accuracy. In contrast, MPNSTs and schwannomas were less reliably distinguished. Given the difficulties in clinically evaluating PNST and in distinguishing benign PNST from MPNST, FDG PET imaging should be used for diagnostic intervention planning and for optimizing treatment strategies.

Malignant peripheral nerve sheath tumour (MPNST): the clinical implications of cellular signalling pathways

Malignant peripheral nerve sheath tumour (MPNST) is a rare malignancy accounting for 3–10% of all soft tissue sarcomas. Most MPNSTs arise in association with peripheral nerves or deep neurofibromas and may originate from neural crest cells, although the specific cell of origin is uncertain. Approximately half of MPNSTs occur in the setting of neurofibromatosis type 1 (NF1), an autosomal dominant disorder with an incidence of approximately one in 3500 persons; the remainder of MPNSTs develop sporadically. In addition to a variety of clinical manifestations, approximately 8–13% of NF1 patients develop MPNSTs, which are the leading cause of NF1-related mortality. Surgical resection is the mainstay of MPNST clinical management. However, because of invasive growth, propensity to metastasise, and limited sensitivity to chemotherapy and radiation, MPNST has a guarded to poor prognosis. Five-year survival rates of only 20–50% indicate an urgent need for improved therapeutic approaches. Recent work in this field has identified several altered intracellular signal transduction cascades and deregulated tyrosine kinase receptors, posing the possibility of personalised, targeted therapeutics. However, expanded knowledge of MPNST molecular pathobiology will be needed to meaningfully apply such approaches for the benefit of afflicted patients.

[Peripheral nerve tumors]

Peripheral nerve tumors are most often benign tumors of the nerve sheath; uncommonly they come from the nerve cells or are metastatic tumors. A precise diagnosis is required for well-adapted and effective treatment, as is good knowledge of fibromatosis diseases. In some cases, the diagnosis of the nerve tumor will lead to a diagnosis of phakomatosis. Surgical treatment must be clearly discussed, which, in case of schwannomas gives very good functional results. Primitive malignant tumors remain an unsolved therapeutic problem.

Primary paraspinal malignant peripheral nerve sheath tumor

Malignant peripheral nerve sheath tumors (MPNSTs) are very rare tumors. We experienced a case of MPNST in the cervical paraspinal space which was not associated with neurofibromatosis. The tumor located in left C6-7 foramen and compressed C7 root. The tumor was removed through the occipital triangle. We report a case of the primary cerivcal MPNST in a patient who did not have neurofibromatosis-1.

Diagnosis and management of intracranial malignant peripheral nerve sheath tumors

OBJECTIVE

Intracranial malignant peripheral nerve sheath tumors (MPNSTs) are rare and generally carry a poor prognosis. We have analyzed our experience with MPNSTs and conducted a review of the literature in an attempt to identify a rational approach to the management of these tumors.

METHODS

Eight patients underwent surgical treatment for intracranial MPNSTs during a 10-year period from 1996 to 2005. The general strategy was to perform complete resection whenever possible and to provide adjuvant radiotherapy for residual tumor. Chemotherapy was not used in this group. The clinical, radiological, operative, and pathological findings of the patients were reviewed retrospectively.

RESULTS

Six of the eight patients underwent primary operations; two of the eight patients had previously undergone other transcranial surgery operations. Total tumor resection was achieved in five patients. At this time, two have been recurrence-free for 3.5 and 5 years, respectively, and the other three patients had a mean postoperative survival of 7 months. There was one case of near total (>90%) and two cases of partial (<90%) tumor removal; the postoperative survival rate was 4, 4, and 2 months, respectively. Only two patients in our group accepted radiotherapy after surgery; one survived only 4 months and the other has been recurrence-free for 5 years.

CONCLUSION

MPNSTs are fast-growing, invasive tumors with rather unsatisfactory outcomes. Total surgical resection seems to be the most effective therapeutic method, and radiotherapy may play a role in local control.

Clinical Relevance of Pathological Grades of Malignant Peripheral Nerve Sheath Tumor: A Multi-Institution TMTS Study of 56 Cases in Northern Japan

BACKGROUND

Malignant peripheral nerve sheath tumor (MPNST) is a relatively rare soft tissue tumor, and its clinical relevance of pathological grades remains obscure.

METHODS

Fifty-six cases of MPNST identified from the files of seven oncology centers of the Tohoku Musculoskeletal Tumor Society (TMTS) and National Cancer Center were analyzed for histologic grades, demographics, treatments, and prognostic factors. The average follow-up period was 41 months.

RESULTS

Twenty-two men and 34 women with a mean age of 45 years were involved. Forty-four (78.6%) of 56 tumors were in the lower extremity or trunk. Fifty tumors (89%) were classified as high grade, and the remaining six as low grade. Twenty-one (39.6%) of 53 patients who underwent tumor excision developed local recurrences. An axial site and inadequate surgical margin were defined as risk factors for local recurrence. The overall survival rates of the 56 patients were 55.1% at 3 years and 43.3% at 5 years. Univariate analysis of the 56 patients revealed large-sized tumors, metastasis at presentation, and histologically high grade were significantly associated with poor prognosis. Multivariate analysis revealed a large tumor and metastasis at presentation to be independent prognostic factors.

CONCLUSIONS

The current study involving 56 patients with MPNST showed the aggressive clinical behavior of the tumor. Large-sized tumors, metastasis at presentation, and high histological grade were related to poor prognosis on univariate analysis, but independency of histological grade was still obscure. In the treatment for a large and high-grade MPNST, an alternative strategy should be further considered.

Malignant peripheral nerve sheath tumor arising in association with the sural nerve

Malignant peripheral nerve sheath tumor is a rare sarcoma of peripheral nerves found most often in deep soft tissue. This aggressive tumor is difficult to diagnose clinically and must be surgically excised for therapy. An incisional biopsy will allow for testing and in most cases, diagnosis. The authors present a case of a 39-year-old African American woman with malignant peripheral nerve sheath tumor in association with the sural nerve. The tumor was surgically removed and sent for pathologic studies. The patient reported to her first postoperative appointment and was referred to an oncologist for follow-up. Despite multiple attempts at contacting the patient and explaining the prognosis of the diagnosis, the patient refused further follow-up care including referral to an oncologist.

Malignant peripheral nerve sheath tumors

BACKGROUND

The authors explored the prognostic factors and clinical outcomes of patients who had malignant peripheral nerve sheath tumors (MPNST) with and without neurofibromatosis type 1 (NF-1).

METHODS

Two hundred five patients with localized MPNST who underwent surgery at the Istituto Nazionale per lo Studio e la Cura dei Tumori (Milan, Italy) over 25 years were reviewed. Forty-six patients had concomitant NF-1 syndrome, and 159 patients did not. Local recurrence, distant metastases, and survival rates were studied.

RESULTS

One hundred thirty patients presented with primary disease, and 75 patients had locally recurrent tumors. The disease-specific mortality rate was 43% at 10 years, with a continuously disease-free survival rate of no greater than 40%. Presentation with either primary or recurrent disease, tumor size, and tumor site (trunk vs. extremity) were the strongest independent predictors of survival. Margin status and radiation therapy also played a role, mostly related to their effect on local outcome. Pathologic grade influenced distant metastases, but only a trend for survival could be observed. No significant independent differences between patients with and without NF-1 were observed.

CONCLUSIONS

To the authors' knowledge, this was among the largest single-institution series to date. The results confirmed that patients with MPNST share similar prognostic factors with patients who have other soft tissue sarcomas and have some of the worst clinical outcomes. The presence of NF-1 syndrome per se did not affect survival, but patients with NF-1 were more likely to have larger tumors. Therefore, such patients should be followed carefully to detect disease as early as possible.

Pediatric malignant peripheral nerve sheath tumor: the Italian and German soft tissue sarcoma cooperative group

PURPOSE

To assess the value of chemotherapy and radiotherapy in children with malignant peripheral nerve sheath tumors (MPNSTs) and to identify risk factors associated with outcome.

PATIENTS AND METHODS

A total of 167 untreated eligible patients enrolled onto the Italian and German studies between 1975 and 1998 entered this analysis. Seventeen percent of patients had neurofibromatosis type 1 (NF1). Chemotherapy was administered to 74% of patients; radiotherapy was administered to 38% of patients.

RESULTS

With a median follow-up of 7 years, 5-year overall survival (OS) and progression-free survival (PFS) were 51% and 37%, respectively. The 5-year OS and PFS by Intergroup Rhabdomyosarcoma Study (IRS) groupings were as follows: group I, 82% and 61%; group II, 62% and 37%; group III, 32% and 27%; group IV, 26% and 21%, respectively. Univariate analysis identified IRS groups, size, invasiveness, primary site, age, and presence of NF1 as prognostic factors; multivariate analysis identified absence of NF1, tumor invasiveness T1, IRS groups I to II and extremity of primary site as independent favorable factors for OS. A trend was observed toward a benefit from radiotherapy after initial gross resection. The overall response rate to primary chemotherapy, including minor responses, in group III patients was 45%.

CONCLUSION

MPNST is an aggressive tumor for which complete surgical resection is the mainstay of successful treatment. Postoperative radiotherapy may have a role in improving local control in patients with minimal residual tumor. The reported responses to primary chemotherapy suggest that it may be effective in patients with tumor considered unresectable at diagnosis.

Survival data for patients with malignant schwannoma

Malignant schwannomas are uncommon sarcomas that arise from the sheath of Schwann surrounding peripheral nerve fibers. These tumors may arise spontaneously in adult patients or may occur with reportedly increased frequency in patients with neurofibromatosis Type I. The tumors have had a reputation for malignancy with rapid metastasis, especially when they arise in relation to neurofibromatosis. We have reviewed the experience of the connective tissue oncology unit with patients with these tumors during the past 25 years. There were 80 malignant schwannomas identified in 41 females and 39 males with a mean age of 36 +/- 17 years. The largest numbers of tumors were seen in the thigh, shoulder, and pelvis but they also occurred in more central (abdomen and thorax) and distal (forearm, hand and foot) locations. The Musculoskeletal Tumor Society stages showed that the majority of the patients had Stage II (high grade but not metastasized) tumors; however, additionally, 10 of the patients had metastases at outset (Stage III). Patient gender was not a factor but stage was a notable determinant of survival. Anatomic location also had a significant effect. Overall, the entire series of patients had a survival of 85% at 11 +/- 5 years and even more remarkable was the fact that there was no difference between the numbers and outcome statistics for tumors arising spontaneously and those occurring in patients with neurofibromatosis.

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 fibrous histiocytoma: an institutional review

BACKGROUND

A thorough understanding of malignant fibrous histiocytoma (MFH), the most common subtype of soft tissue sarcoma, will lead to improved histologic-specific protocols.

METHODS

126 patients with histologically confirmed MFH were analyzed. The median follow-up was 42 months (range 1-233 months).

RESULTS

Overall survival was 58% at 5 years and 38% at 10 years. Grade significantly influenced prognosis, with 10-year survival of 90%, 60%, and 20% for low, intermediate, and high grade tumors, respectively (p = 0.0007). Distant metastases at initial presentation (p = 0.0002) and size of the primary tumor (p = 0.0007) influenced outcome. Neither anatomic site nor depth of the primary tumor were significant prognostic factors. Positive microscopic margins were associated with a decreased disease-free survival (p = 0.006).

CONCLUSIONS

Tumor grade, size, and distant metastases at initial presentation remain the most important prognostic factors for MFH. Resection with negative microscopic margins decreased the incidence of local recurrence.

Soft tissue sarcoma involving the sciatic nerve

In the Clinical Dilemma slot the editors pose a question to an acknowledged expert in the field. In this issue we address the problem of a sarcoma in the posterior aspect of the thigh. At operation, despite preoperative magnetic resonance imaging, the lesion is unexpectedly found to involve the sciatic nerve. How should one proceed? Professor Murray Brennan of New York replies.

Malignant peripheral nerve sheath tumors in the setting of segmental neurofibromatosis. Case report

Approximately 100 cases of segmental neurofibromatosis (NF5) have been reported in the recent literature. Patients with NF5 present with café-au-lait macules, freckles, and/or neurofibromas limited to one or adjacent dermatomes. Neurofibromas arising in NF5 have been uniformly considered to be benign; patients were thought to have an excellent prognosis without the risk of developing malignant peripheral nerve sheath tumors (PNSTs), which are characteristic in patients with the generalized form of this disease, von Recklinghausen's NF. In this report the authors detail the first observations of malignant PNSTs in two patients with NF5. Indications for surgical removal of a neurofibroma in a patient with NF include pain. neurological impairment, compression of adjacent structures, cosmetic disfigurement, and rapid tumor growth suggestive of malignant degeneration. Surgical indications are similar for patients with NF5. All patients with neurofibromas should be considered at risk for malignant degeneration.

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.