High-grade Malignant Peripheral Nerve Sheath Tumors Research Articles

A rare Encounter with Pediatric Malignant Peripheral Nerve Sheath Tumor in Nasal Sinuses and Orbit.

This case report explores a rare and aggressive Malignant Peripheral Nerve Sheath Tumor (MPNST) in a 7-year-old child affecting nasal sinuses, maxilla, and orbit, an exceptionally uncommon pediatric manifestation unrelated to Neurofibromatosis 1. The child presented with alarming symptoms-nasal obstruction, snoring, epistaxis, and difficulty swallowing-underscoring the case's urgency. Non-contrast computed tomography revealed an extensive mass infiltrating nasopharynx, nasal cavity, maxillary sinus, ethmoid sinuses, and orbit, causing destructive consequences. Histopathology confirmed a high-grade MPNST, marked by rapid growth and early metastasis, highlighting management challenges. The rarity of pediatric MPNST in the nasal cavity is discussed, emphasizing the need for a broad differential diagnosis. Treatment involves surgical resection and adjuvant chemoradiation with a grim prognosis due to diagnostic complexities and morphological mimicry in young patients.

Magnetic Resonance Imaging Features for Differentiating Low-Grade and High-Grade Malignant Peripheral Nerve Sheath Tumors.

This study aimed to assess the usefulness of magnetic resonance imaging (MRI) findings for differentiating low-grade and high-grade malignant peripheral nerve sheath tumors (MPNSTs). This study included 31 patients (onset age range, 19-83 years; mean onset age, 57 years; 9 men and 22 women) with 36 histopathologically proven MPNSTs (7 low-grade MPNSTs and 29 high-grade MPNSTs) who underwent preoperative MRI between December 2007 and October 2022. Quantitative and qualitative MRI findings were retrospectively evaluated and compared between the 2 subtypes. The maximum tumor diameter (106.1 ± 64.0 vs 54.9 ± 19.8 mm, P = 0.032) and tumor-to-muscle signal intensity ratio (SIR) of fat-suppressed gadolinium-enhanced T1-weighted images (2.69 ± 1.40 vs 1.62 ± 0.40, P = 0.005) were significantly higher in high-grade MPNSTs than in low-grade MPNSTs. The receiver operating characteristic analysis revealed that the tumor-to-muscle SIR of fat-suppressed gadolinium-enhanced T1-weighted images exhibited the highest area under the curve value (0.88), followed by the maximum tumor diameter (0.76). The sensitivity and specificity of the tumor-to-muscle SIR of fat-suppressed gadolinium-enhanced T1-weighted images for diagnosing high-grade MPNST at an optimal SIR threshold of greater than 1.73 were 90% and 83%, respectively. However, other MRI findings showed no significant differences between the 2 subtypes ( P = 0.16-1.00). Although the MRI findings of low-grade and high-grade MPNST overlapped considerably, the maximum tumor diameter and degree of contrast enhancement can be used to differentiate low-grade MPNST from high-grade MPNST.

Analysis of H3k27me3 Expression in Malignant Peripheral Nerve Sheath Tumor (MPNST) and Other Spindle Cell Sarcoma Mimicking MPNST

Malignant Peripheral Nerve Sheath Tumor (MPNST) is a type of spindle cell sarcoma with approximately 5% of all sarcomas. Its diagnosis is challenging due to the absence of specific immunohistochemical markers. Recently, H3K27me3 was discovered as a potential specific immunohistochemical marker to differentiate MPNST from other sarcomas and distinguish between low and high-grade MPNST. Therefore, this research aims to investigate the use of the H3K27me3 as a potential specific marker for Malignant Peripheral Nerve Sheath Tumor (MPNST). A cross-sectional analysis was conducted on 50 cases of sarcomas, including 13 MPNST, 14 synovial sarcomas, 13 dermatofibrosarcoma protuberans (DFSP), and 10 leiomyosarcomas originating from the Department of Anatomical Pathology, Faculty of Medicine, Universitas Indonesia, Cipto Mangunkusumo Hospital (FMUI-CMH) from January 2013 to December 2021. H3K27me3 images were obtained and categorized as complete loss when more than 95% of the tumor cells showed loss of nuclear staining. The results found in MPNST showed a loss of H3K27me3 expression, which is statistically significant compared to other sarcomas mimicking MPNST (p=0.021), indicating its potential as a diagnostic marker. There is a difference in the expression of H3K27me3 between the high and low-grade MPNST but it is not statistically significant (p=0.105). This showed that H3K27me3 loss of expression can be used to diagnose MPNST, especially high-grade MPNST, and differentiate it from other sarcomas mimicking MPNST.

A pilot study of lenvatinib plus pembrolizumab in patients with advanced sarcoma.

11517 Background: New treatment options are needed for sarcomas. Lenvatinib (L) is an oral, multi-tyrosine kinase inhibitor with significant inhibitory activity against VEGF receptor (VEFGR) 1-3, FGF receptor (FGFR) 1-3, KIT, platelet-derived growth factor receptor (PDGFR) alpha/beta, and RET. Experimental models suggest that L can favorably alter the tumor immune environment, and the combination of L and pembrolizumab (P) has proven to be synergistic and effective across multiple solid tumor types, providing rationale for this study. Methods: This is a pilot study evaluating the efficacy of L and P in select sarcomas. Patients who had at least 1 prior regimen but ≤ 3 were enrolled into one of five cohorts (n = 10 each) A: leiomyosarcoma (LMS); B: undifferentiated pleomorphic sarcoma (UPS); C: angiosarcoma and epithelioid hemangioendothelioma (EHE); D: synovial sarcoma (SS) and malignant peripheral nerve sheath tumor (MPNST); and E: osteosarcoma (OS) and chondrosarcoma (CS). Patients were treated with an initial 2-week run-in of L 20 mg orally daily. Subsequently, P was administered at 200 mg IV every 21 days. The primary endpoint for each cohort was the best objective response rate (ORR) documented by RECIST v1.1 by 27 weeks. The combination was considered worthy of further study if 2 or more responses were observed in a cohort. Secondary endpoints included progression-free survival (PFS), overall survival, duration of response, and safety of the combination. Archival tissue and on-treatment biopsies were collected. Results: As of January 31st, 2023, cohorts A, D and E have completed accrual. The best response in the LMS cohort was stable disease (SD). In cohort D there were 3 partial responses (PR): 2 SS; 1 radiation associated high grade MPNST. In cohort E one of 6 patients with OS had a PR. To date, of the 6 patients with angiosarcoma, there was 1 PR in a patient with adrenal primary that occurred after the prespecified 27-week timepoint. One of 5 evaluable patients in Cohort B had a PR. Among the 44 patients evaluable for safety, most common AEs were hypertension (56.8%), diarrhea (45.5%), proteinuria (45.5%), fatigue (40.9%), headache (36.4%) and nausea (36.4%). Most common ≥ grade 3 AEs were hypertension (13.6%), dyspnea (6.8%), non-cardiac chest pain (6.8%), syncope (6.8%). Conclusions: A signal of activity was noted in this pilot study for patients with OS, MPNST, angiosarcoma and SS. In the LMS cohort, there were no responses, and PFS was poor. Enrollment to cohorts B and C is ongoing. Clinical trial information: NCT04784247 . [Table: see text]

Resurfacing the defect from wide excision of a malignant peripheral nerve sheath tumor based on a thoracodorsal artery perforator free flap: a case report

Malignant peripheral nerve sheath tumors (MPNSTs) are rare, aggressive soft tissue sarcomas with a high rate of recurrence and metastasis. Limb salvage surgery with free flap reconstruction is a viable option for selected patients with MPNSTs, but careful consideration should be given to the risk of recurrence. This case report describes a 26-year-old male patient with a recurrent, aggressive, high-grade MPNST who underwent limb salvage surgery with thoracodorsal artery perforator free flap reconstruction. Despite the surgical intervention, local recurrence of the MPNST was detected, and below-knee amputation was ultimately recommended. This case highlights the importance of early, definitive treatment decision-making in cases of aggressive, high-grade MPNSTs. Close postoperative monitoring and early detection of recurrence are crucial for achieving optimal outcomes in patients with MPNSTs undergoing limb salvage surgery with free flap reconstruction.

Malignant peripheral nerve sheath tumor in children: A clinicopathologic and molecular study with parallels to the adult counterpart.

Malignant peripheral nerve sheath tumors (MPNST) are aggressive neoplasms, arising either sporadically, in the setting of neurofibromatosis type I (NF1) or post radiation. Most MPNST occur in adults and their pathogenesis is driven by the loss of function mutations in the PRC2 complex, regardless of their clinical presentation. In contrast, pediatric MPNST are rare and their pathogenesis has not been elucidated. In this study, we investigate a large cohort of 64 MPNSTs arising in children and young adults (younger than the age of 20 years) to better define their clinicopathologic and molecular features. Sixteen (25%) cases were investigated by MSK-IMPACT, a targeted NGS panel of 505 cancer genes. Most patients (80%) were aged 11-20 years. A history of NF1 was established in half of the cases. Mean tumor size was 8.5cm. The most common locations included the extremities (34%) and abdomen/pelvis (27%). Histologically, 89% of high-grade MPNST showed conventional features, while the remaining three cases showed a predominant epithelioid phenotype. Heterologous differentiation occurred in 25% of high grade cases, with half showing rhabdomyoblastic differentiation. Tumors arose in a background of a plexiform neurofibroma (16%), neurofibroma (13%), and schwannoma in two cases (3%). Immunohistochemically, H3K27me3 expression was lost in 82% of conventional high-grade MPNST analyzed, while loss of SMARCB1 expression was seen in one epithelioid MPNST. Genomically, all cases showed more than one genetic abnormality, with 53% showing mutations in EED / SUZ12 genes, and 47% of cases harboring alterations in NF1 and CDKN2A/CDKN2B genes. At the last follow-up, 30% patients died of disease, 28% were alive with disease and 42% had no evidence of disease. NF1 status did not correlate with overall survival. In conclusion, half of pediatric and young adult MPNST were NF1-related and showed loss of function alterations in PRC2 complex, NF1, and CDKN2A, similar to the adult counterpart. Thus, H3K27me3 loss of expression may be used in the diagnosis of high grade MPNSTs in children. Moreover, a small subset of pediatric MPNST have an epithelioid morphology with different pathogenesis.

Prevalence and detection of actionable BRAF V600 and NRAS Q61 mutations in malignant peripheral nerve sheath tumor by droplet digital PCR

Malignant peripheral nerve sheath tumors ( MPNSTs) are aggressive tumors with poor prognosis that do not typically respond well to standard chemotherapy. Recently, point mutations involving BRAF V600E have been demonstrated in a subset of MPNST, offering the possibility of targeted treatment. However, the reported prevalence of these alterations is variable. Mutations involving NRAS, which is also involved in the MAPK/ERK pathway and amenable to targeted inhibitors, have not been well characterized in MPNST. In this study, we validated droplet digital polymerase chain reactionfor the detection of BRAF V600E and NRAS Q61 mutations and evaluate the prevalence of BRAF V600E and NRAS Q61 mutations in 79 cases of MPNST, including 45 sporadic, 27 NF-1 associated, and 7 radiation-associated tumors. We detected actionable BRAF or NRAS mutations in 3 of 44sporadic MPNSTs (6.8%), including 2 BRAFV600 and 1 NRAS Q61 mutations, as well as 1 NRAS Q61 mutation in a tumor that was ultimately considered to represent melanoma. These 3 cases with positive mutations were exclusively in sporadic, high-grade MPNST (FNCLCC grade 3 of 3), with a prevalence of 11.5% in this group (3.8% NRAS Q61 mutations and 7.7% BRAF V600 mutations). None of the tumors associated with NF-1 or prior radiation had detectable mutations in the genes tested. Overall, the prevalence of these alterations offers the possibility of targeted therapy in this aggressive type of sarcoma and suggests the potential benefit of routine clinical testing.

1534 A rare operation: resection of a complex malignant peripheral nerve sheath tumour deemed inoperable by a national centre

Abstract We present this rare case which was led by spinal surgeons at Leeds after being deemed not suitable for operative input by a national centre. A 54-year-old lady who presented with 2-month history of worsening left flank pain on a background of four years. She was otherwise fit and well. CT confirmed aggressive left-sided paraspinal tumour with epidural encroachment, extending from T8 to T10 vertebral levels. Its deep surface was well-defined and extending superficially through the chest wall with destruction of ribs. The mass grew in size in course of days requiring urgent attention due to risk of cord compression. Biopsy proved high grade MPNST. Malignant peripheral nerve sheath tumor (MPNST) is a rare type of sarcoma, 5-10% of sarcoma cases. MPNST is most common in young adults and middle-aged adults. About 25% to 50% of people with MPNST have NF1. 8% to 13% of people with NF1 will get MPNST in their lifetime. An MDT approach involving spinal, thoracic, vascular and plastic surgeons opined it requiring extensive surgery due to its complexity. It was performed in stages – embolisation then aortic stent placement followed by final resection of the tumour with chest well reconstruction using an LD flap. A multidisciplinary and multispecialty approach has led to a positive prognosis for this patient who is on the road to recovery.

Assessment of H3K27me3 immunohistochemistry and combination of NF1 and p16 deletions by fluorescence in situ hybridization in the differential diagnosis of malignant peripheral nerve sheath tumor and its histological mimics

BackgroundA definitive diagnosis of malignant peripheral nerve sheath tumor (MPNST) is challenging, especially in cases without neurofibromatosis 1 (NF1), because MPNST lacks specific markers on immunohistochemistry (IHC).MethodsWe performed IHC for histone 3 trimethylated on lysine 27 (H3K27me3) and evaluated the percentage of cells with H3K27me3 loss using measured values at 10% intervals, categorized as complete loss (100% of tumor cells lost staining), partial loss (10% to 90% of tumor cells lost staining), and intact (no tumor cells lost staining). We conducted fluorescence in situ hybridization (FISH) for NF1 and p16 deletions comparing 55 MPNSTs and 35 non-MPNSTs, consisting of 9 synovial sarcomas (SSs), 8 leiomyosarcomas (LMSs), 10 myxofibrosarcomas (MFSs), and 8 undifferentiated pleomorphic sarcomas (UPSs). We assessed the percentage of cells with homozygous and heterozygous deletions and defined “deletion” if the percentage of either the NF1 or p16 deletion signals was greater than 50% of tumor cells.ResultsAmong the 55 MPNSTs, 23 (42%) showed complete H3K27me3 loss and 32 (58%) exhibited partial loss or intact. One each of the 9 SSs (11%), 8 LMSs (12%), and 8 UPSs (12%) showed complete H3K27me3 loss and many non-MPNSTs exhibited intact or partial H3K27me3 loss. Among the 55 MPNSTs, 33 (60%) and 44 (80%) showed NF1 or p16 deletion, respectively. Co-deletion of NF1 and p16 was observed in 29 (53%) MPNSTs. Among the 23 MPNTSs showing H3K27me3 complete loss, 18 (78%) and 20 (87%) exhibited NF1 or p16 deletion, respectively. Among the 32 MPNSTs with H3K27me3 partial loss or intact, 15 (47%) and 24 (75%) exhibited NF1 or p16 deletion, respectively. The frequency of NF1 and/or p16 deletion tended to be lower in non-MPNSTs than in MPNSTs. Approximately 90% of MPNSTs included cases with H3K27me3 complete loss and cases showing H3K27me3 partial loss or intact with NF1 and/or p16 deletion. Approximately 50% of MPNSTs showed co-deletion of NF1 and p16 regardless of H3K27me3 loss.ConclusionsFISH for NF1 and p16 deletions, frequently observed in high-grade MPNSTs, might be a useful ancillary diagnostic tool for differentiating MPNST from other mimicking spindle cell and pleomorphic sarcomas.

Differences in MMP-2 Expression in High- and Low-Grade MPNST and its Correlation with Prognostic Factors

Malignant peripheral nerve sheath tumor (MPNST) is a soft tissue sarcoma, which is difficult to distinguish from other spindle cell sarcomas. MPNST is hostile, with a high recurrence, and tends to metastasize hematogenously, especially to the lungs. A phase of the metastasis is a degradation of the extracellular matrix, where Matrix Metalloproteinase (MMP) plays an essential role in this process. Gelatinase-type MMP, MMP-2 and MMP-9, can degrade basal membrane and fibrillar collagen to open the invasion pathway. MMP-2 can degrade more collagen and non-collagen extracellular matrix than MMP-9. Therefore, the study aimed to see the relationship between MMP-2 overexpression and histopathological malignancy grading and other clinical prognostic variables. The study was conducted by immunohistochemical staining of MMP-2 in 39 cases, consisting of 19 cases of low-grade MPNST and 20 cases of high-grade MPNST. Subsequently, an analysis of the relationship between MMP-2 overexpression and the malignancy grading and clinical variables was performed, such as age, sex, and tumor size and location. MMP-2 overexpression was seen in 19 (95%) cases of high grade and three (15.8%) cases of low-grade MPNST (p 0.000). The study also found a significant relationship between MMP-2 overexpression and histopathology grading, which may be helpful to define the prognosis.

TMOD-06. MALIGNANT TRANSFORMATION OF PLEXIFORM NEUROFIBROMAS IN AN NF1 MUTANT MOUSE MODEL OF SPINAL IRRADIATION

Abstract PURPOSE Understanding the relationships between ionizing radiation (IR) and carcinogenesis, as well as other variables, including genetic background and sex, may minimize risks of transformation from benign to aggressive cancers while maintaining treatment efficacy. We aim to understand the relationship between IR, tumor microenvironments, and effect of sex on malignant transformation using a conditional knockout mouse model of Neurofibromatosis type 1 (NF1). METHODS Conditional knockout mouse models of plexiform neurofibromas (PeriCre+; Nf1fl/fl and PeriCre+; Nf1fl/-, n = 172) were treated with 0 Gy; 3 Gy x 5; 3 Gy x 10 of focal, fractionated spinal irradiation (SI) and aged until signs of illness. Histopathological analysis was performed on images from H&E-stained FFPE peripheral nerve tissues. RESULTS SI affected the survival of mice in a dose-dependent manner, with a significant decrease at 30Gy (median survival 254 and 218 days for 0 Gy and 30 Gy, p < 0.01, Log-rank test). Male mice had reduced overall survival at 15 and 30 Gy (median survival 368, 278 and 245 days for 0, 15 and 30Gy, p < 0.01, Log-rank test), but not in female mice, indicating sex-specific radiosensitivity. Differences in tumour microenvironments did not affect mouse survival after SI. Histopathological analysis is ongoing (43 out of 76 FFPE samples analyzed). Preliminary findings showed a total of 43 malignancies ranging from plexiform neurofibromas (PNs) to high-grade malignant peripheral nerve sheath tumours (MPNSTs). Increasing histologic aggressiveness was observed in higher SI doses, with high-grade MPNST (2.3%) exclusively found in mice irradiated at 30 Gy. CONCLUSION We present a novel mouse model to study malignant transformation in the context of NF1. Preliminary findings suggest increased malignant transformation at high doses of SI.

The Value of H3K27me3 Immunohistochemistry in Differentiating Malignant Peripheral Nerve Sheath Tumour with Its Histologic Mimickers.

Background:Diagnosis of malignant peripheral nerve sheath tumor (MPNST) is rather challenging due to its divergent morphologic heterogeneity and lack of specific ancillary test. The emergence of H3K27 trimethylation (H3K27me3) as a new immunohistochemistry (IHC) marker for MPNST have recently available to assist pathologists in differentiating MPNST from other histologic mimics. We aim to study the expression pattern of H3K27me3 in MPNST and its histologic mimickers and their association with the clinicopathological data. Methodology:A total of 59 benign and malignant spindle cell tumours (18 MPNST and 41 of its histologic mimickers which included 10 schwannoma, 13 neurofibroma, 4 synovial sarcoma, 3 fibrosarcoma, 2 gastrointestinal stromal tumour (GIST), 4 leiomyosarcoma, 1 spindle cell liposarcoma, 1 solitary fibrous tumour, 2 low grade fibromyxoid sarcoma and 1 unclassified spindle cell sarcoma), diagnosed from January 1998 to April 2018 in Hospital Universiti Sains Malaysia (HUSM) were tested for H3K27me3 by IHC. The MPNST histological grade was assessed based on the French Fe’de’ ration Nationale des Centres de LutteContre le Cancer (FNCLCC) for 3 tiers system (low grade, intermediate grade and high grade). The clinicopathological data were retrieved from the patients’ record. Results:A total of 61.1% (11/18 MPNST) showed loss of H3K27me3 expression which is statistically significant as compared to its histologic mimics (p<0.001). Similar findings (p=0.026) were also observed in high grade MPNST (81.8%), intermediate grade MPNST (100%) and 0% in low grade MPNST. Conclusion: H3K27me3, combined with other panel of markers, is useful in MPNST diagnosis to differentiate it from the histological mimickers.

H3K27 trimethylation loss in malignant peripheral nerve sheath tumor: a systematic review and meta-analysis with diagnostic implications.

Multiple studies have reported the loss of trimethylation at lysine (K) 27 on histone 3 (H3K27me3) in high-grade malignant peripheral nerve sheath tumors (MPNSTs). However, the diagnostic potential of this finding in MPNSTs remains yet to be fully substantiated. Correspondingly, our aim was to pool systematically-identified metadata in the literature and substantiate the incidence of H3K27me3 loss in this setting. Searches of 7 electronic databases from inception to May 2019 were conducted following PRISMA guidelines. Articles were screened against pre-specified criteria. The incidence of loss was then pooled by random-effects meta-analysis of proportions. Nine pertinent studies described a total of 823 high-grade MPNST samples. When pooled, incidence (sensitivity) of complete H3K27me3 loss was estimated to be 53% (95% CI 42-64%). For MPNST subtypes, estimated incidences of complete loss in NF1 subtype was 52% (95% CI 41-62), in sporadic subtype was 53% (95% CI 36-70%), in the epithelioid subtype was 0% (95% CI 0-7%), and radiation-associated subtype was 98% (95% CI 86-100%). Finally, incidence of incomplete loss (specificity) in 1231 MPNST-mimic samples was estimated to be 96% (95% CI 90-99%). Certainty of these outcomes ranged from very low to high. The incidence of complete H3K27me3 loss is substantial in high-grade MPNSTs and is low in MPNST-mimics. Greater cohort study and biological investigation will validate the certainty of these findings as well as elucidate their true molecular and clinical significances.

Synchronous Development of Multicentric Malignant Peripheral Nerve Sheath Tumors: Institutional Review

Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft tissue sarcomas, with approximately 50% occurring in patients diagnosed with neurofibromatosis type 1 (NF-1). NF-1 occurs in approximately 1/3000 individuals, and given that the lifetime prevalence of MPNST is estimated at 8%-13%, synchronous development of separate MPNSTs is plausible. We sought to report the incidence of synchronous MPNST in a cohort of pathology-proven cases since1994. Records since 1994 were queried and identified 192 patients with pathology-proven MPNST. Medical records of these patients were reviewed to search for patients with synchronous MPNSTs. Retrospective review of 192 patients treated for MPNST at our institution (including 71 patients with NF-1) revealed only 1 patient with synchronous MPNSTs. A 48-year-old woman with NF-1 presented with progressive right upper and lower extremity pain and radicular symptoms. Biopsies of right sciatic and median nerve lesions revealed high-grade MPNST, and she underwent radiotherapy and complete resection of both masses. Due to initial nonspecific biopsy results and patient preference, treatment of the median nerve lesion was delayed by 8 months. She did not have recurrence of her disease at the 18-month follow-up. Synchronous development of MPNST is unusual, with an incidence of 1.4% in our cohort of NF-1 patients with MPNSTs. Given the reported incidence of synchronous MPNST, the rate of malignant transformation in NF-1 may be overestimated. However, heightened suspicion for malignant transformation should continue in patients harboring a diagnosis of MPNST.

The implications of intradural extension in paraspinal malignant peripheral nerve sheath tumors: effects on central nervous system metastases and overall survival.

OBJECTIVEIn this study, the authors sought to compare tumors with intradural extension to those remaining in the epidural or paraspinal space with the hypothesis that intradural extension may be a mechanism for seeding of the CSF with malignant cells, thereby resulting in higher rates of CNS metastases and shorter overall survival.METHODSThe authors searched the medical record for cases of malignant peripheral nerve sheath tumors (MPNSTs) identified from 1994 to 2017. The charts of the identified patients were then reviewed for tumor location to identify patients with paraspinal malignancy. All patients included in the study had tumor specimens that were reviewed in the surgical pathology department. Paraspinal tumors with intradural extension were identified in the lumbar, sacral, and spinal accessory nerves, and attempts were made to match this cohort to another cohort of patients who had paraspinal tumors of the cranial nerves and lumbar and sacral spinal regions without intradural extension. Further information was collected on all patients with and without intradural extension, including date of diagnosis by pathology specimen review; nerve or nerves of tumor origin; presence, location, and diagnostic date of any CNS metastases; and either the date of death or date of last follow-up.RESULTSThe authors identified 6 of 179 (3.4%) patients who had intradural tumor extension and compared these patients with 12 patients who harbored paraspinal tumors that did not have intradural extension. All tumors were diagnosed as high-grade MPNSTs according to the surgical pathology findings. Four of 6 (66.7%) patients with intradural extension had documented CNS metastases. The presence of CNS metastases was significantly higher in the intradural group than in the paraspinal group (intradural, 66.7% vs paraspinal, 0%; p < 0.01). Time from diagnosis until death was 11.2 months in the intradural group and approximately 72 months in the paraspinal, extradural cohort.CONCLUSIONSIn patients with intradural extension of paraspinal MPNSTs, significantly higher rates of CNS metastases are seen with a reduced interval of time from diagnosis to metastatic lesion detection. Intradural tumor extension is also a poor prognostic factor for survival, with these patients showing a reduced mean time from diagnosis to death.

Malignant peripheral nerve sheath tumor: Transformation in a patient with neurofibromatosis type 2

Malignant peripheral nerve sheath tumor (MPNST) is a rare soft-tissue sarcoma with an unfavorable prognosis and limited therapeutic options. MPNSTs can be sporadic, but are often associated with neurofibromatosis (NF) 1 and usually arise from preexisting neurofibromas. MPNSTs in patients with NF2 have been reported in only exceedingly rare cases, and the mechanisms underlying transformation into an MPNST have not been fully elucidated. Here, we describe the clinicopathological and genomic features of a peripheral nerve sheath tumor (PNST), with a primary diagnosis of a neurofibroma, as it transforms into a high-grade MPNST in the context of NF2.

Extensive perineural spread of an intrapelvic sciatic malignant peripheral nerve sheath tumor: a case report

Perineural spread has been described in multiple neoplasms of neural and non-neural origin. The peripheral nervous system may represent a highway by which tumors can spread throughout the body. Malignant peripheral nerve sheath tumor (MPNST) is a neoplasm arising from peripheral nerves with high rates of local recurrence and distant metastases, leading to a poor 5-year overall survival. In many cases, the optimal treatment involves wide en bloc excision with negative margins as well as chemotherapy and radiation. Even in cases of negative surgical margins, recurrence rates are high, suggesting possible skip lesions or very distant infiltration along the involved nerve. We report a case of high-grade MPNST of the sciatic nerve with post-mortem dissection and histopathologic characterization of perineural spread of microscopic disease to sites significantly proximal and distal to areas with evidence of gross disease, which may help to explain the high rates of local and distal recurrence in MPNST.

Abstract 681: Using a genome-editing approach for the stepwise establishment of zebrafish models of pediatric high-grade gliomas and MPNSTs

Abstract By high-throughput sequencing of cancer patient's genomes, driver mutations have recently been described in high-grade pediatric glioma, an aggressive type of brain tumor in children. The most prominent recurrent mutations were found in four genes, namely NF1, TP53, ATRX and H3F3A. NF1 and TP53 are tumor suppressor genes and their loss of function is characteristic for various human malignancies. However, the mechanisms through which precise missense mutations in H3F3A and loss-of-function of ATRX influence tumor biology remain largely unknown. In our project, we employ the genome-editing technology CRISPR-Cas9 to develop a zebrafish model of pediatric high-grade glioma, in order to examine the impact of these mutations on tumor onset and progression. We previously created a zebrafish line that is deficient for tp53 (tp53-/-) and has a loss-of-function mutation in 3 of 4 alleles of nf1 (nf1a+/-, nf1b-/-), which is duplicated in zebrafish. These fish develop high-grade gliomas with low penetrance and malignant peripheral nerve sheath tumors (MPNSTs) with high penetrance. By CRISPR-Cas9 we further incorporated early frameshift mutations of atrx in the background of tp53-/-, nf1a+/-, nf1b-/-. All analyzed fish injected with Cas9-mRNA and CRISPR guide-RNAs (gRNAs) targeting atrx coding sequences showed germline transmission of mutant alleles, of which one third were frameshift mutations. Primary CRISPR-Cas9 atrx-gRNA injected tp53-/-, nf1a+/-, nf1b-/- fertilized eggs developed as mosaics and exhibited increased tumor penetrance and faster onset of MPNSTs and these tumors harbored atrx mutations in 8/10 analyzed samples. This indicates that atrx loss-of-function mutations cooperate with loss of tp53 and nf1 tumor suppressors. Gliomas were not observed in mosaic atrx mutated fish, and these will be reanalyzed in stable atrx mutant lines. Next, we will add previously described missense mutations of h3f3a. To unravel the synergy between oncogenic mutations in atrx and h3f3a in tumor progression, mutant stable lines for both genes will be investigated independently and in a combined manner. The zebrafish model of pediatric high-grade gliomas and MPNSTs that we are developing will be useful to dissect the mechanisms underlying cooperation among driver mutations and for small molecule screens to identify specific inhibitors of cell growth and survival in these malignancies. Citation Format: Felix Oppel, Shuning He, Ting Tao, Mark W. Zimmerman, Adam D. Durbin, Nina Weichert, Dong H. Ki, A Thomas Look. Using a genome-editing approach for the stepwise establishment of zebrafish models of pediatric high-grade gliomas and MPNSTs. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 681.

Methylation-based classification of benign and malignant peripheral nerve sheath tumors

The vast majority of peripheral nerve sheath tumors derive from the Schwann cell lineage and comprise diverse histological entities ranging from benign schwannomas and neurofibromas to high-grade malignant peripheral nerve sheath tumors (MPNST), each with several variants. There is increasing evidence for methylation profiling being able to delineate biologically relevant tumor groups even within the same cellular lineage. Therefore, we used DNA methylation arrays for methylome- and chromosomal profile-based characterization of 171 peripheral nerve sheath tumors. We analyzed 28 conventional high-grade MPNST, three malignant Triton tumors, six low-grade MPNST, four epithelioid MPNST, 33 neurofibromas (15 dermal, 8 intraneural, 10 plexiform), six atypical neurofibromas, 43 schwannomas (including 5 NF2 and 5 schwannomatosis associated cases), 11 cellular schwannomas, 10 melanotic schwannomas, 7 neurofibroma/schwannoma hybrid tumors, 10 nerve sheath myxomas and 10 ganglioneuromas. Schwannomas formed different epigenomic subgroups including a vestibular schwannoma subgroup. Cellular schwannomas were not distinct from conventional schwannomas. Nerve sheath myxomas and neurofibroma/schwannoma hybrid tumors were most similar to schwannomas. Dermal, intraneural and plexiform neurofibromas as well as ganglioneuromas all showed distinct methylation profiles. Atypical neurofibromas and low-grade MPNST were indistinguishable with a common methylation profile and frequent losses of CDKN2A. Epigenomic analysis finds two groups of conventional high-grade MPNST sharing a frequent loss of neurofibromin. The larger of the two groups shows an additional loss of trimethylation of histone H3 at lysine 27 (H3K27me3). The smaller one retains H3K27me3 and is found in spinal locations. Sporadic MPNST with retained neurofibromin expression did not form an epigenetic group and most cases could be reclassified as cellular schwannomas or soft tissue sarcomas. Widespread immunohistochemical loss of H3K27me3 was exclusively seen in MPNST of the main methylation cluster, which defines it as an additional useful marker for the differentiation of cellular schwannoma and MPNST.

Giant sporadic high-grade malignant peripheral nerve sheath tumor: A case report with review of literature

Malignant peripheral nerve sheath tumors (MPNSTs) are uncommon spindle cell sarcomas originating from the pleuripotent cells of neural crest or Schwann cells. Head and neck region, the extremities and peripheral nerve trunk roots are its common locations. Sporadic type is a rare variant than the neurofibromatosis-1 associated type of MPNST. This study presents a case of giant, sporadic, and high-grade MPNST of right shoulder in a 48-year-old female.