Contemporary Approach to Neurofibromatosis Type 1-Associated Malignant Peripheral Nerve Sheath Tumors

Most malignant peripheral nerve sheath tumors (MPNSTs) are clinically aggressive high-grade sarcomas, arising in individuals with neurofibromatosis type 1 (NF1) at a significantly elevated estimated lifetime frequency of 8%-13%. In the setting of NF1, MPNSTs arise from malignant transformation of benign plexiform neurofibroma and borderline atypical neurofibromas. Composed of neoplastic cells from the Schwannian lineage, these cancers recur in approximately 50% of individuals, and most patients die within five years of diagnosis, despite surgical resection, radiation, and chemotherapy. Treatment for metastatic disease is limited to cytotoxic chemotherapy and investigational clinical trials. In this article, we review the pathophysiology of this aggressive cancer and current approaches to surveillance and treatment.

Recurrent sporadic malignant triton tumor in the carotid sheath in the absence of neurofibromatosis

Malignant Triton Tumors (MTTs) are a rare and aggressive subtype of malignant peripheral nerve sheath tumors (MPNSTs), often associated with neurofibromatosis type 1. This case report describes a unique instance of recurrent sporadic MTT within the carotid sheath in a 33-year-old male without any personal or familial history of neurofibromatosis. The patient initially presented with a biopsy-confirmed MTT in the right neck, involving the carotid body and brachial plexus, and underwent partial resection, radiation therapy, and chemotherapy. Six months later, the patient presented with recurrent MTT, and subsequently underwent radical tumor resection, segmental right carotid artery resection, and deep femoral vein interposition. Recovery was complicated by hematoma formation, and the patient developed vocal fold paralysis and a left vocal fold cyst, necessitating further surgeries. Yearly follow-ups for 8 years revealed no recurrence. This case emphasizes the importance of comprehensive patient evaluation, including clinical history, imaging, and biopsy findings, for accurate diagnosis and prompt surgical intervention in managing such rare and aggressive tumors. Further research is needed to identify novel therapies and improve survival rates for patients with MTTs.

Decorin suppresses stemness and migration potential of malignant peripheral nerve sheath tumor through inhibiting epidermal growth factor receptor signaling

Cancer stem cells (CSCs) play pivotal roles in the growth, invasion, metastasis, chemo-resistance in malignant peripheral nerve sheath tumor (MPNST). The current characterization of CSCs in MPNST is not complete. Decorin is a critical regulator of microenvironment, but its expression and function in CSCs of MPNST has not been studied. In the current study, Decorin levels and its relationship with lung and liver metastasis were determined in clinical specimens. Decorin expression in CD133-positive or CD44-positive CSCs was analyzed by RT-qPCR on cytospun MPNST cells after flow cytometry-based cell sorting. Decorin-positive cells were separated from Decorin-negative cells in transfected MPNST cell lines using a designed plasmid expressing red fluorescent protein (RFP) under a Decorin promoter. Tumor sphere formation, tumor growth, cell invasion, cell migration, and the resistance to chemotherapy-induced apoptosis were determined on Decorin-positive versus Decorin-negative MPNST cells. In vivo tumor growth was analyzed in mice receiving subcutaneous transplantation of Decorin-positive versus Decorin-negative MPNSTs. We found that Decorin levels were significantly downregulated in MPNST specimens, compared to non-tumorous adjacent tissue. Significantly lower Decorin levels were detected in MPNSTs with lung or liver metastasis compared to those without. Poorer patient survival was detected in Decorin-low MPNST, compared to Decorin-high subjects. More Decorin-negative cells were detected in CD133-positive MPNST cells than CD133-negative MPNST cells, and in CD44-positive MPNST cells than in CD44-negative MPNST cells. Compared to Decorin-positive MPNST cells, Decorin-negative MPNST cells generated significantly more tumor spheres in culture, were more invasive and migratory, and were more resistant to chemotherapy-induced apoptosis, likely due to the inhibition of epidermal growth factor receptor signaling by Decorin. Decorin-negative MPNST cells grew significantly larger tumor in vivo. Thus, depletion of Decorin may occur in CSCs in MPNSTs, serving possibly as a new therapeutic target.

Low-grade malignant peripheral nerve sheath tumour presenting as retroperitoneal spindle cell neoplasm

Retroperitoneal spindle cell neoplasms are diagnostically challenging. Malignant peripheral nerve sheath tumours (MPNSTs) can sometimes present as sporadic primary retroperitoneal tumours. MPNSTs are usually high-grade and highly aggressive tumours and are associated with a poor prognosis. Low-grade MPNSTs are very rarely described. This current case report describes a case of sporadic primary low-grade MPNST presenting as retroperitoneal spindle cell neoplasm. The diagnosis, imaging and immunohistopathological findings, as well as its successful surgical management, are presented.

PRRX1-TOP2A interaction is a malignancy-promoting factor in human malignant peripheral nerve sheath tumours

BACKGROUND

Paired related-homeobox 1 (PRRX1) is a transcription factor in the regulation of developmental morphogenetic processes. There is growing evidence that PRRX1 is highly expressed in certain cancers and is critically involved in human survival prognosis. However, the molecular mechanism of PRRX1 in cancer malignancy remains to be elucidated.

METHODS

PRRX1 expression in human Malignant peripheral nerve sheath tumours (MPNSTs) samples was detected immunohistochemically to evaluate survival prognosis. MPNST models with PRRX1 gene knockdown or overexpression were constructed in vitro and the phenotype of MPNST cells was evaluated. Bioinformatics analysis combined with co-immunoprecipitation, mass spectrometry, RNA-seq and structural prediction were used to identify proteins interacting with PRRX1.

RESULTS

High expression of PRRX1 was associated with a poor prognosis for MPNST. PRRX1 knockdown suppressed the tumorigenic potential. PRRX1 overexpressed in MPNSTs directly interacts with topoisomerase 2 A (TOP2A) to cooperatively promote epithelial-mesenchymal transition and increase expression of tumour malignancy-related gene sets including mTORC1, KRAS and SRC signalling pathways. Etoposide, a TOP2A inhibitor used in the treatment of MPNST, may exhibit one of its anticancer effects by inhibiting the PRRX1-TOP2A interaction.

CONCLUSION

Targeting the PRRX1-TOP2A interaction in malignant tumours with high PRRX1 expression might provide a novel tumour-selective therapeutic strategy.

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

OBJECTIVE

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).

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

p53 modulates kinase inhibitor resistance and lineage plasticity in NF1-related MPNSTs

Malignant peripheral nerve sheath tumors (MPNSTs) are chemotherapy resistant sarcomas that are a leading cause of death in neurofibromatosis type 1 (NF1). Although NF1-related MPNSTs derive from neural crest cell origin, they also exhibit intratumoral heterogeneity. TP53 mutations are associated with significantly decreased survival in MPNSTs, however the mechanisms underlying TP53-mediated therapy responses are unclear in the context of NF1-deficiency. We evaluated the role of two commonly altered genes, MET and TP53, in kinome reprograming and cellular differentiation in preclinical MPNST mouse models. We previously showed that MET amplification occurs early in human MPNST progression and that Trp53 loss abrogated MET-addiction resulting in MET inhibitor resistance. Here we demonstrate a novel mechanism of therapy resistance whereby p53 alters MET stability, localization, and downstream signaling leading to kinome reprogramming and lineage plasticity. Trp53 loss also resulted in a shift from RAS/ERK to AKT signaling and enhanced sensitivity to MEK and mTOR inhibition. In response to MET, MEK and mTOR inhibition, we observed broad and heterogeneous activation of key differentiation genes in Trp53-deficient lines suggesting Trp53 loss also impacts lineage plasticity in MPNSTs. These results demonstrate the mechanisms by which p53 loss alters MET dependency and therapy resistance in MPNSTS through kinome reprogramming and phenotypic flexibility.

Malignant peripheral nerve sheath tumour with divergent epithelioid differentiation in a cat

Divergent differentiation, mainly towards various subsets of mesenchymal cells, is encountered sporadically in human malignant peripheral nerve sheath tumours (MPNSTs) but this is the first report of epithelioid components within this neoplasm in a cat. An 8-year-old, spayed female Domestic Shorthaired cat was presented for surgical removal of a subcutaneous mass on the right flank. Morphological and immunohistochemical analysis revealed a malignant neoplasm with spindloid cells intermixed with an epithelioid component that had squamous differentiation. There was intense immunolabelling of vimentin, S100 protein, neuron-specific enolase, laminin and glial fibrillary acidic protein in the spindloid cell component and for cytokeratin (CK) AE1/AE3 and CK5/6 in the epithelial elements. Melanoma-associated antigen, desmin, α-smooth muscle actin, CD18, CD31, ionized calcium binding adapter molecule-1 and CK8/18 were not expressed, which helped differentiate the tumour from other feline spindloid cell neoplasms. These features are characteristic of divergent epithelioid differentiation of MPNST.

[Successful surgical excision of a melanoma and a rare peripheral nerve sheath tumor in 2 cattle]

A heifer and a dairy cow were presented to our practice with cutaneous masses on the left side of their necks. Each mass had a diameter of approximately 20 cm. Both tumors had increased in size in recent weeks and were now prone to injuries from the stable equipment. Both animal owners agreed to surgical removal, which was performed under sedation and local anesthesia on a bovine treatment crush. The subsequent histopathological examinations of the extirpates revealed a melanocytoma in the young heifer and a cutaneous peripheral nerve sheath tumor (PNST) in the dairy cow. Both cases were benign tumors. The postoperative course was without complications and no recurrences were observed even more than a year later. No comparable tumors were found in related animals or in the offspring.

Coefficient of variation of T2-weighted MRI may predict the prognosis of malignant peripheral nerve sheath tumor

BACKGROUND

We investigated whether non-enhancement MRI features, including measurement of the heterogeneity of the tumor with MR T2 imaging by calculating coefficient of variation (CV) values, were associated with the prognosis of non-metastatic malignant peripheral nerve sheath tumors (MPNST).

METHODS

This retrospective study included 42 patients with MPNST who had undergone surgical resection (mean age, 50 years ± 21; 20 male participants). Non-enhancement MR images were evaluated for signal intensity heterogeneity on T1- and T2-weighted imaging, tumor margin definition on T1- and T2-weighted imaging, peritumoral edema on T2-weight imaging, and CV. We measured the signal intensities of MR T2-weighted images and calculated the corresponding CV values. CV is defined as the ratio of the standard deviation to the mean. The associations between factors and overall survival (OS) were investigated via the Kaplan-Meier method with log-rank tests and the Cox proportional hazards model.

RESULTS

The mean CV value of MR T2 images was 0.2299 ± 0.1339 (standard deviation) (range, 0.0381-0.8053). Applying receiver operating characteristics analysis, the optimal cut-off level for CV value was 0.137. This cut-off CV value was used for its stratification into high and low CV values. At multivariate survival analysis, a high CV value (hazard ratio = 3.63; 95% confidence interval = 1.16-16.0; p = 0.047) was identified as an independent predictor of OS.

CONCLUSION

The CV value of the signal intensity of heterogenous MPNSTs MR T2-weighted images is an independent predictor of patients' OS.

Shaping Our Understanding of Malignant Peripheral Nerve Sheath Tumor: A Bibliometric Analysis of the 100 Most-Cited Articles

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNSTs) are rare yet highly aggressive soft tissue sarcomas of mesenchymal origin, characterized by a heterogeneous pathological spectrum, limited therapeutic options, and high metastatic potential.

METHODS

Here, the authors conducted a comprehensive bibliometric analysis of the 100 most-cited MPNST articles by utilizing Elsevier's Scopus to identify all relevant published and indexed articles referring to MPNST, thereby aiming to elucidate the pertinent research findings regarding the disease's pathophysiology and therapeutic advancements. Articles were classified as basic science or clinical and analyzed for various bibliometric parameters.

RESULTS

The majority of articles (75%) focused on clinical aspects, reflecting the extensive clinicopathological characterization of MPNSTs. Notable studies investigated prognostic factors, histological and immunohistochemical features, and diagnostic modalities. The identification of loss of function mutations in the polycomb repressive complex 2 emerged as a pivotal role, as it opened avenues for potential targets for novel therapeutic interventions. Newer articles (published in or after 2006) demonstrated higher citation rates, suggesting evolving impact and collaboration.

CONCLUSIONS

This bibliometric analysis showed how developments in the understanding of MPNST pathophysiology and the creation of novel therapeutic strategies occurred throughout time. Changes that have been noticed recently could portend future innovative therapeutic approaches.

MRI features of benign peripheral nerve sheath tumors: how do sporadic and syndromic tumors differ?

OBJECTIVES

To compare MRI features of sporadic and neurofibromatosis syndrome-related localized schwannomas and neurofibromas.

METHODS

In this retrospective study, our pathology database was searched for "neurofibroma" or "schwannoma" from 2014 to 2019. Exclusion criteria were lack of available MRI and intradural or plexiform tumors. Qualitative and quantitative anatomic (location, size, relationship to nerve, signal, muscle denervation) and functional (arterial enhancement, apparent diffusion-weighted coefficient) MRI features of sporadic and syndrome-related tumors were compared. Statistical significance was assumed for p < 0.05.

RESULTS

A total of 80 patients with 64 schwannomas (sporadic: 42 (65.6%) v. syndrome-related: 22 (34.4%)) and 19 neurofibromas (sporadic: 7 (36.8%) v. syndrome-related: 12 (41.7%)) were included. Only signal heterogeneity (T2W p=0.001, post-contrast p=0.03) and a diffused-weighted imaging target sign (p=0.04) were more frequent with schwannomas than neurofibromas. Sporadic schwannomas were similar in size to syndrome-related schwannomas (2.9±1.2cm vs. 3.7±3.2 cm, p = 0.6), but with greater heterogeneity (T2W p = 0.02, post-contrast p = 0.01). Sporadic neurofibromas were larger (4.6±1.5cm vs. 3.4±2.4 cm, p = 0.03) than syndrome-related neurofibromas, also with greater heterogeneity (T2W p=0.03, post-contrast p=0.04). Additional tumors along an affected nerve were only observed with syndrome-related tumors). There was no difference in apparent diffusion coefficient values or presence of early perfusion between sporadic and syndrome-related tumors (p > 0.05).

CONCLUSIONS

Although syndrome-related and sporadic schwannomas and neurofibromas overlap in their anatomic, diffusion and perfusion features, signal heterogeneity and presence of multiple lesions along a nerve are differentiating characteristics of syndrome-related tumors.

Expanding a precision medicine platform for malignant peripheral nerve sheath tumors: New patient-derived orthotopic xenografts, cell lines and tumor entities

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive soft-tissue sarcomas with a poor survival rate, presenting either sporadically or in the context of neurofibromatosis type 1 (NF1). The histological diagnosis of MPNSTs can be challenging, with different tumors exhibiting great histological and marker expression overlap. This heterogeneity could be partly responsible for the observed disparity in treatment response due to the inherent diversity of the preclinical models used. For several years, our group has been generating a large patient-derived orthotopic xenograft (PDOX) MPNST platform for identifying new precision medicine treatments. Herein, we describe the expansion of this platform using six primary tumors clinically diagnosed as MPNSTs, from which we obtained six additional PDOX mouse models and three cell lines, thus generating three pairs of in vitro-in vivo models. We extensively characterized these tumors and derived preclinical models, including genomic, epigenomic, and histological analyses. Tumors were reclassified after these analyses: three remained as MPNSTs (two being classic MPNSTs), one was a melanoma, another was a neurotrophic tyrosine receptor kinase (NTRK)-rearranged spindle cell neoplasm, and, finally, the last was an unclassifiable tumor bearing neurofibromin-2 (NF2) inactivation, a neuroblastoma RAS viral oncogene homolog (NRAS) oncogenic mutation, and a SWI/SNF-related matrix-associated actin-dependent regulator of chromatin (SMARCA4) heterozygous truncated variant. New cell lines and PDOXs faithfully recapitulated histology, marker expression, and genomic characteristics of the primary tumors. The diversity in tumor identity and their specific associated genomic alterations impacted treatment responses obtained when we used the new cell lines for testing compounds against known altered pathways in MPNSTs. In summary, we present here an extension of our MPNST precision medicine platform, with new PDOXs and cell lines, including tumor entities confounded as MPNSTs in a real clinical scenario. This platform may constitute a useful tool for obtaining correct preclinical information to guide MPNST clinical trials.

STING activation reprograms the microenvironment to sensitize NF1-related malignant peripheral nerve sheath tumors for immunotherapy

Neurofibromatosis type 1 (NF1) is caused by mutations in the NF1 gene that encodes neurofibromin, a RAS GTPase-activating protein. Inactivating NF1 mutations cause hyperactivation of RAS-mediated signaling, resulting in the development of multiple neoplasms, including malignant peripheral nerve sheath tumors (MPNSTs). MPNSTs are an aggressive tumor and the main cause of mortality in patients with NF1. MPNSTs are difficult to resect and refractory to chemo- and radiotherapy, and no molecular therapies currently exist. Immune checkpoint blockade (ICB) is an approach to treat inoperable, undruggable cancers like MPNST, but successful outcomes require an immune cell-rich tumor microenvironment. While MPNSTs are noninflamed "cold" tumors, here, we converted MPNSTs into T cell-inflamed "hot" tumors by activating stimulator of IFN genes (STING) signaling. Mouse genetic and human xenograft MPNST models treated with a STING agonist plus ICB exhibited growth delay via increased apoptotic cell death. This strategy offers a potential treatment regimen for MPNSTs.

Malignant peripheral nerve sheath tumor in the kidney of a dog

A 12-year-old castrated male poodle presented with vomiting and diarrhea. Ultrasonography and computed tomography revealed a protruding mass at the caudal pole of the left kidney. Grossly, the poorly circumscribed abnormal mass was 1.6 × 1.8 × 1.9 cm in size and had multifocal dark-red foci. Microscopically, it was composed of densely or loosely packed variable-sized short spindle or ovoid cells. These neoplastic cells showed high pleomorphism, mitotic figures, and invasive tendency to the adjacent tissue. Immunohistochemically, the neoplastic spindle cells expressed vimentin, S100, neuron-specific enolase, nerve growth factor receptor, and laminin. Therefore, the mass was diagnosed as a malignant peripheral nerve sheath tumor (MPNST). To our knowledge, this is the first report of primary renal MPNST in a dog.

Intramuscular Hybrid Nerve Sheath Tumor of the Thigh: Case Report and Literature Review

BACKGROUND/AIM

Hybrid nerve sheath tumor (HNST) is a benign peripheral nerve sheath tumor with combined features of more than one histological type, such as schwannoma, neurofibroma, and perineurioma. It remains under-recognized in routine clinical practice. Herein, we describe an unusual case of intramuscular HNST of the thigh.

CASE REPORT

The patient was a 41-year-old man with no history of trauma who presented with a 3-month history of a palpable mass in the right thigh. Physical examination revealed a 4-cm, elastic hard, mobile, nontender mass. Magnetic resonance imaging exhibited a well-circumscribed intramuscular mass with low-to-intermediate signal intensity on T1-weighted sequences and higher signal intensity peripherally and lower signal intensity centrally, representing a target sign, on T2-weighted sequences. Complete surgical excision of the tumor was carried out. Microscopically, the tumor showed dual histological components of both schwannoma and neurofibroma. Immunohistochemically, the schwannomatous component was strongly and diffusely positive for S-100 protein and negative for CD34, while the neurofibromatous component contained CD34-positive fibroblasts and S-100 protein-positive Schwann cells. Epithelial membrane antigen was negative for both components. These findings were consistent with a diagnosis of HNST (hybrid schwannoma/neurofibroma). The patient had no evidence of local recurrence and no neurological deficit at the final follow-up.

CONCLUSION

Although extremely rare, HNST should be included in the extended differential diagnosis of a well-circumscribed, intramuscular soft-tissue mass in the extremities, particularly in young and early middle-aged adults.

Role of catecholamine synthases in the maintenance of cancer stem-like cells in malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are malignant tumors that are derived from Schwann cell lineage around peripheral nerves. As in many other cancer types, cancer stem cells (CSCs) have been identified in MPNSTs, and they are considered the cause of treatment resistance, recurrence, and metastasis. As an element defining the cancer stemness of MPNSTs, we previously reported a molecular mechanism by which exogenous adrenaline activates a core cancer stemness factor, YAP/TAZ, through β2 adrenoceptor (ADRB2). In this study, we found that MPNST cells express catecholamine synthases and that these enzymes are essential for maintaining cancer stemness, such as the ability to self-renew and maintain an undifferentiated state. Through gene knockdown and inhibition of these enzymes, we confirmed that catecholamines are indeed synthesized in MPNST cells. The results confirmed that catecholamine synthase knockdown in MPNST cells reduces the activity of YAP/TAZ. These data suggest that a mechanism of YAP/TAZ activation by de novo synthesized adrenaline, as well as exogenous adrenaline, may exist in the maintenance of cancer stemness of MPNST cells. This mechanism not only helps to understand the pathology of MPNST, but could also contribute to the development of therapeutic strategies for MPNST.

Systematic Characterization of the Clinical and Pathological Features of Schwannomas Harboring SH3PXD2A::HTRA1 Fusion

The understanding of schwannoma tumorigenesis has been reshaped by the recent identification of SH3PXD2A::HTRA1 fusion in 10% of intracranial/spinal schwannomas. Nonetheless, pathologic features of schwannomas harboring this fusion, as well as its prevalence outside intracranial/spinal locations, have not been characterized. We screened 215 consecutive schwannomas for their clinicopathologic characteristics and fusion status using reverse-transcriptase polymerase chain reaction (RT-PCR). Among 29 (13.5%) fusion-positive schwannomas, the most prevalent location was peripheral somatic tissue (30.7%, 19/62), followed by spinal/paraspinal (18.4%, 7/38), body cavity/deep structures (10%, 2/20), intracranial (1.3%, 1/75), and viscera (0/13). All 8 cellular, 4 microcystic/reticular, and 3 epithelioid schwannomas were fusion-negative, as were 41/42 nonschwannomatous peripheral nerve sheath tumors. Remarkably, a distinct 'serpentine' palisading pattern, comprising ovoid/plump cells shorter than usual schwannian cells in a hyalinized stroma, was identified in most fusion-positive cases and the schwannomatous component of the only fusion-positive malignant peripheral nerve sheath tumor. To validate this finding, 60 additional cases were collected, including 36 with (≥10% arbitrarily) and 24 without appreciable serpentine histology, of which 29 (80.6%) and 2 (8.3%) harbored the fusion, respectively. With percentages of 'serpentine' areas scored, 10% was determined as the optimal practical cut-off to predict the fusion status (sensitivity, 0.950; specificity, 0.943). Fusion positivity was significantly associated with serpentine histology, smaller tumors, younger patients, and peripheral somatic tissue, while multivariate logistic linear regression analysis only identified serpentine histology and location as independent fusion-predicting factors. RNA in situ hybridization successfully detected the fusion junction, highly concordant with RT-PCR results. Gene expression profiling on 18 schwannomas demonstrated segregation largely consistent with fusion status. Fusion-positive cases expressed significantly higher HTRA1 mRNA abundance, perhaps exploitable as a biomarker. In summary, we systematically characterize a series of 60 SH3PXD2A::HTRA1 fusion-positive schwannomas, showing their distinctive morphology and location-specific prevalence for the first time.

Malignant triton tumor of uterus: A case report and literature review

Malignant triton tumor (MTT) is a highly aggressive malignant neoplasm, classified as a variant of malignant peripheral nerve sheath tumor with rhabdomyoblastic differentiation. There are few reports that MTT occurred in urogenital system. In the present study, we report the first MTT occurring in the uterus. A 57-year-old woman came to the emergency department due to persistent vaginal bleeding for 2 months. The gynecological palpation found that a club-shaped excrescence existed in the vagina about 7 cm × 3 cm × 3 cm. The mass located in the lower segment of the uterus and the cervix was confirmed by gynecological vaginal ultrasound and magnetic resonance imaging, which was preliminarily diagnosed as cervical carcinoma. After neoplasm punch biopsy, the pathological diagnosis was malignant triton tumor. The patient finally lost follow-up. This is the first report about MTT in the uterus and suggests that pathological biopsy combined with imaging examination is necessary for the diagnosis of rarely MTT.

[Interdisciplinary Treatment Of Tumorous And Tumour-Like Lesions Of Peripheral Nerves]

Tumorous or tumour-like lesions of peripheral nerves are generally rare, heterogeneous and challenging to diagnose and treat. They may become apparent by a palpable swelling (lump) near nerves, sensory and/or motor deficits, pain to touch or neuropathic pain. In 91% of cases, tumours are benign. The differentiation of entities and their characteristics as well as a function-preserving resection strategy are highly relevant. Misdiagnosis and inadequate treatment can lead to severe deficits and pain syndromes. Benign tumours include schwannomas and neurofibromas, which can occur sporadically but can also be associated with neurogenetic tumour disposition syndromes if they occur more frequently. Rarer benign nerve tumours include perineuriomas, lipomas, aggressive fibrosis (desmoid tumours), paragangliomas and haemangiomas. Ganglion cysts are described as tumour-like lesions. The association of nerve tumours with neurogenetic syndromes and the correct classification of potentially malignant lesions such as MPNST (malignant peripheral nerve sheath tumour) or intermediate stages such as ANNUBPs (atypical neurofibromatous neoplasms with unknown biological potential) pose particular challenges. Interdisciplinarity is highly relevant for clinical treatment and a correct diagnosis. The aim of our work is to provide an overview of the relevant entities, diagnostic evaluation and contemporary treatment strategies based on the current data situation and taking into account the recently published interdisciplinary AWMF S2k guideline "Diagnosis and Treatment of Peripheral Nerve Tumours".

A Case of Superficial Papular Neuroma: A Rare Neural Neoplasm

ABSTRACT

A case of 67-year-old male patient with superficial papular neuroma (SPN) on the occiput is reported. This is the second report of SPN and the first with clinical images. Histologically, in the superficial dermis and periadnexa, the specimen exhibits a nodule of bland spindle cells with an S-shaped and spindle nucleus, surrounded by eosinophilic collagen fibers and scattered mast cells, which forms focally peripheral nerve-like structures. Lichen simplex chronicus-like changes are observed. Immunostaining result revealed that the tumor cells are positive for S-100, neurofilament, collagen IV, and CD34 but negative for Melan A, epithelial membrane antigen, and glial fibrillary acidic protein. Histological differential diagnosis includes prurigo nodularis, neurotized nevus, benign peripheral nerve sheath tumor, such as neurofibroma or schwannoma, a type of neuroma, such as traumatic neuroma, mucosal neuroma, and palisaded encapsulated neuroma, or a type of neural hamartoma. A careful histological investigation will enable dermatopathologists to make a diagnosis of SPN.

Asymmetry of thalamic hypometabolism on FDG-PET/CT in neurofibromatosis type 1: Association with peripheral tumor burden

BACKGROUND AND PURPOSE

Thalamic hypometabolism is a consistent finding in brain PET with F-18 fluorodeoxyglucose (FDG) in patients with neurofibromatosis type 1 (NF1). However, the pathophysiology of this metabolic alteration is unknown. We hypothesized that it might be secondary to disturbance of peripheral input to the thalamus by NF1-characteristic peripheral nerve sheath tumors (PNSTs). To test this hypothesis, we investigated the relationship between thalamic FDG uptake and the number, volume, and localization of PNSTs.

METHODS

This retrospective study included 22 adult NF1 patients (41% women, 36.2 ± 13.0 years) referred to whole-body FDG-PET/contrast-enhanced CT for suspected malignant transformation of PNSTs and 22 sex- and age-matched controls. Brain FDG uptake was scaled voxelwise to the individual median uptake in cerebellar gray matter. Bilateral mean and left-right asymmetry of thalamic FDG uptake were determined using a left-right symmetric anatomical thalamus mask. PNSTs were manually segmented in contrast-enhanced CT.

RESULTS

Thalamic FDG uptake was reduced in NF1 patients by 2.0 standard deviations (p < .0005) compared to controls. Left-right asymmetry was increased by 1.3 standard deviations (p = .013). Thalamic hypometabolism was higher in NF1 patients with ≥3 PNSTs than in patients with ≤2 PNSTs (2.6 vs. 1.6 standard deviations, p = .032). The impact of the occurrence of paraspinal/paravertebral PNSTs and of the mean PNST volume on thalamic FDG uptake did not reach statistical significance (p = .098 and p = .189). Left-right asymmetry of thalamic FDG uptake was not associated with left-right asymmetry of PNST burden (p = .658).

CONCLUSIONS

This study provides first evidence of left-right asymmetry of thalamic hypometabolism in NF1 and that it might be mediated by NF1-associated peripheral tumors.

Peripheral nerve tumors

The chapter is focused on the neoplastic peripheral nerve lesions, which primarily involve "cranial and paraspinal nerves," as outlined in the CNS volume (WHO_Classification_of_Tumours_Editorial_Board, 2021). These include classic peripheral nerve sheath tumors such as schwannoma, neurofibroma, intraneural perineurioma, and malignant peripheral nerve sheath tumors, with their variants as well as new and more precisely defined entities, including hybrid nerve sheath tumors and malignant melanotic nerve sheath tumor (previously melanotic schwannoma).

[Malignant melanotic nerve sheath tumor of the posterior mediastinum]

Melanotic schwannoma (MS) is a rare and infrequent subtype of schwannoma characterized by cytoplasmic deposits of melanosomes (melanin). Unlike the other schwannomas, it could have malignant transformation. Due to distinctive characteristics and atypical behavior from classic schwannomas subtypes, MS were renamed and reclassified as "melanocytic malignant neural sheath tumor" in the 5th ed. of the World Health Organization's classification of central nervous system tumors in 2021. We present two cases of MS that underwent complete surgical resection.

Malignant and Benign Peripheral Nerve Sheath Tumors in a Single Center: Value of Clinical and Ultrasound Features for the Diagnosis of Malignant Peripheral Nerve Sheath Tumor Compared With Magnetic Resonance Imaging

OBJECTIVES

This study aimed to investigate the combined use of ultrasonography and clinical features for the differentiation of malignant peripheral nerve sheath tumors (MPNST) from benign peripheral nerve sheath tumors (BPNST) and to compare the efficacy of ultrasonography with that of magnetic resonance imaging (MRI).

METHODS

This retrospective study included 28 MPNSTs and a control group of 57 BPNSTs. All patients underwent an ultrasound scan using the Logiq E9 (GE Health Care, Milwaukee, WI) or EPIQ7 equipment (Philips Medical System, Bothell, WA). A 3.0-T MRI machine (Ingenia; Philips Healthcare, Best, the Netherlands) was used for scanning, and conventional MRI was performed on different regions based on the patient's clinical situation. The following variables were evaluated: palpable mass, pain, nerve symptoms, maximum diameter, location, shape, boundary, encapsulation, echogenicity, echo homogeneity, presence of a cystic component, calcification, target sign, posterior echo, and intertumoral vascularity of the tumors. The diagnostic efficacy of ultrasonography and clinical factors was compared with that of MRI. Independent factors for predicting MPNST versus BPNST were also assessed.

RESULTS

The parameters of location, shape, boundary, encapsulation, and vascularity were significantly different between MPNSTs and BPNSTs. Multiple logistic regression analysis showed that shape, boundary, and vascularity were independent predictors of MPNSTs. The sensitivity, specificity, and Youden index of the three clinical and ultrasound factors (shape, boundary, and vascularity) were 0.89, 0.81, and 0.69, respectively, whereas those of MRI were 0.71, 0.89, and 0.61, respectively. No significant differences in the area under the curve (AUC) of the three combined clinical and ultrasound factors and those of MRI were found (P > .05).

CONCLUSIONS

MRI was useful in the differential diagnosis between MPNSTs and BPNSTs. However, the combination of clinical and ultrasound diagnoses can achieve the same effect as MRI, including shape, boundary, and vasculature.

Surgical and oncologic outcomes in dogs with malignant peripheral nerve sheath tumours arising from the brachial or lumbosacral plexus

Malignant peripheral nerve sheath tumours (MPNST) of a plexus nerve or nerve root cause significant morbidity and present a treatment challenge. The surgical approach can be complex and information is lacking on outcomes. The objective of this study was to describe surgical complication rates and oncologic outcomes for canine MPNST of the brachial or lumbosacral plexus. Dogs treated for a naïve MPNST with amputation/hemipelvectomy with or without a laminectomy were retrospectively analysed. Oncologic outcomes were disease free interval (DFI), overall survival (OS), and 1- and 2-year survival rates. Thirty dogs were included. The surgery performed was amputation alone in 17 cases (57%), and amputation/hemipelvectomy with laminectomy in 13 cases (43%). Four dogs (13%) had an intraoperative complication, while 11 dogs (37%) had postoperative complications. Histologic margins were reported as R0 in 12 dogs (40%), R1 in 12 dogs (40%), and R2 in five dogs (17%). No association was found between histologic grade and margin nor extent of surgical approach and margin. Thirteen dogs (46%) had recurrence. The median DFI was 511 days (95% CI: 140-882 days). The median disease specific OST was 570 days (95% CI: 467-673 days) with 1- and 2-year survival rates of 82% and 22% respectively. No variables were significantly associated with recurrence, DFI, or disease specific OST. These data show surgical treatment of plexus MPNST was associated with a high intra- and postoperative complication rate but relatively good disease outcomes. This information can guide clinicians in surgical risk management and owner communication regarding realistic outcomes and complications.

Epithelioid malignant peripheral nerve sheath tumour of the ulnar nerve around the elbow: a diagnostic and therapeutic challenge

Epithelioid malignant peripheral nerve sheath tumour (EMPNST) is a rare histological subtype of malignant peripheral nerve sheath tumour (MPNST), accounting for 5% to 17% of MPNSTs. The clinical and MRI findings of EMPNST mimic those of nerve abscesses, similar to the presentation in Hansen's disease. We present one such case with this kind of diagnostic dilemma. Intraoperative findings suggest a tumour changed the course of management subsequently. The development of neurological deficits postoperatively after tumour resection was a reconstructive challenge. To provide motor power and sensation through a procedure that provides a complete functional outcome for a young patient, distal nerve transfers were chosen. This provided an improvement in the quality of life and hastened the neurological recovery of the involved limb. Level of evidence: V.

Ex vivo to in vivo model of malignant peripheral nerve sheath tumors for precision oncology

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNST) are aggressive soft tissue sarcomas that often develop in patients with neurofibromatosis type 1 (NF1). To address the critical need for novel therapeutics in MPNST, we aimed to establish an ex vivo 3D platform that accurately captured the genomic diversity of MPNST and could be utilized in a medium-throughput manner for drug screening studies to be validated in vivo using patient-derived xenografts (PDX).

METHODS

Genomic analysis was performed on all PDX-tumor pairs. Selected PDX were harvested for assembly into 3D microtissues. Based on prior work in our labs, we evaluated drugs (trabectedin, olaparib, and mirdametinib) ex vivo and in vivo. For 3D microtissue studies, cell viability was the endpoint as assessed by Zeiss Axio Observer. For PDX drug studies, tumor volume was measured twice weekly. Bulk RNA sequencing was performed to identify pathways enriched in cells.

RESULTS

We developed 13 NF1-associated MPNST-PDX and identified mutations or structural abnormalities in NF1 (100%), SUZ12 (85%), EED (15%), TP53 (15%), CDKN2A (85%), and chromosome 8 gain (77%). We successfully assembled PDX into 3D microtissues, categorized as robust (>90% viability at 48 h), good (>50%), or unusable (<50%). We evaluated drug response to "robust" or "good" microtissues, namely MN-2, JH-2-002, JH-2-079-c, and WU-225. Drug response ex vivo predicted drug response in vivo, and enhanced drug effects were observed in select models.

CONCLUSIONS

These data support the successful establishment of a novel 3D platform for drug discovery and MPNST biology exploration in a system representative of the human condition.

A malignant peripheral nerve-sheath tumor: A CARE case report

INTRODUCTION

Malignant peripheral nerve-sheath tumor (MPNST) is an extremely rare sarcoma of the nasal cavity and paranasal sinuses. Non-specific clinical and radiological presentation and challenging histological diagnosis make it little known by physicians. We describe a case of maxillary sinus MPNST, following CARE guidelines.

CASE REPORT

A 62-year-old woman consulted for swelling of the right cheek and hard palate with several months' progression. CT and MRI revealed a tissue mass in the right maxillary sinus with osteolysis of the orbital and maxillary floors, hard palate and lateral and medial walls of the maxillary sinus. Biopsy confirmed diagnosis of low-grade MPNST. After total resection and 60Gy adjuvant radiotherapy, 2-year follow-up showed no signs of recurrence.

CONCLUSION

MPNST in the nasal cavity and paranasal sinuses is very rare. Because of a high risk of recurrence, wide resection should be implemented, possibly completed by radiotherapy if resection cannot be complete because of proximity to at-risk structures.

Imaging in gynecological disease (26): clinical and ultrasound characteristics of benign retroperitoneal pelvic peripheral-nerve-sheath tumors

OBJECTIVE

To describe the clinical and sonographic characteristics of benign, retroperitoneal, pelvic peripheral-nerve-sheath tumors (PNSTs).

METHODS

This was a retrospective study of patients with a benign, retroperitoneal, pelvic PNST who had undergone preoperative ultrasound examination at a single gynecologic oncology center between 1 January 2018 and 31 August 2022. All ultrasound images, videoclips and final histological specimens of benign PNSTs were reviewed side-by-side in order to: describe the ultrasound appearance of the tumors, using the terminology of the International Ovarian Tumor Analysis (IOTA), Morphological Uterus Sonographic Assessment (MUSA) and Vulvar International Tumor Analysis (VITA) groups, following a predefined ultrasound assessment form; describe their origin in relation to nerves and pelvic anatomy; and assess the association between their ultrasound features and histotopography. A review of the literature reporting benign, retroperitoneal, pelvic PNSTs with preoperative ultrasound examination was performed.

RESULTS

Five women (mean age, 53 years) with a benign, retroperitoneal, pelvic PNST were identified, four with a schwannoma and one with a neurofibroma, of which all were sporadic and solitary. All patients had good-quality ultrasound images and videoclips and final biopsy of surgically excised tumors, except one patient managed conservatively who had only a core needle biopsy. In all cases, the findings were incidental. The five PNSTs ranged in maximum diameter from 31 to 50 mm. All five PNSTs were solid, moderately vascular tumors, with non-uniform echogenicity, well-circumscribed by hyperechogenic epineurium and with no acoustic shadowing. Most of the masses were round (n = 4 (80%)), and contained small, irregular, anechoic, cystic areas (n = 3 (60%)) and hyperechogenic foci (n = 5 (100%)). In the woman with a schwannoma in whom surgery was not performed, follow-up over a 3-year period showed minimal growth (1.5 mm/year) of the mass. We also summarize the findings of 47 cases of benign retroperitoneal schwannoma and neurofibroma identified in a literature search.

CONCLUSIONS

On ultrasound examination, no imaging characteristics differentiate reliably between benign schwannomas and neurofibromas. Moreover, benign PNSTs show some similar features to malignant retroperitoneal tumors. They are solid lesions with intralesional blood vessels and show degenerative changes such as cystic areas and hyperechogenic foci. Therefore, ultrasound-guided biopsy may play a pivotal role in their diagnosis. If confirmed to be benign PNSTs, these tumors can be managed conservatively, with ultrasound surveillance. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Diagnostic Significance of Ki67 Staining Pattern in Benign Peripheral Nerve Sheath Tumors: An Additional Diagnostic Tool

Introduction. Benign peripheral nerve sheath tumors involve mainly neurofibromas, schwannomas, and their variants. Ki67 is a widely used immunohistochemical marker that predicts the proliferation rate of tumors including the nerve sheath-derived neoplasms and it is helpful to differentiate them from their malignant counterparts. However, Ki67 score is not used in distinction of the benign peripheral nerve sheath tumors types from each other. Our aim is to contribute to the literature by identifying the hypothesized specific Ki67 staining patterns of benign peripheral nerve sheath tumors. Methods. Fifty-three tumors (distributed as follows: 26 schwannomas, 24 neurofibromas, and 3 hybrid schwannoma-neurofibroma tumors) from 49 patients were included in the study. Two researchers analyzed the slides independently. Tumors were classified according to their Ki67 staining patterns in 3 different groups: zonal (Z-Ki67), focal zonal or mixed (M-Ki67), and scattered Ki67 (S-Ki67). Results. There was a significant correlation among the types of benign peripheral nerve sheath tumor and the Ki67 staining patterns (P < .01). Level of inter-rater reliability was calculated as good (>0.7) and excellent (>0.8) according to 2 different calculations of kappa score. Conclusions. In conclusion, our study demonstrates that the Ki67 staining pattern may be used as an additional diagnostic tool in the diagnosis of benign peripheral nerve sheath tumors.

Malignant Peripheral Nerve Sheath Tumor in the Nasal Cavity of a Neonate: A Case Report

Malignant peripheral nerve sheath tumor (MPNST) is a rare tumor that can develop on the lining of nerves and within the network of nerve fibers in different organs, and it is commonly found in the head and neck, limbs, and trunk. These tumors can occur in patients of any age. They most commonly occur in adults aged 20 to 50 years; however, fewer cases of this tumor in children have been reported. To date, no neonatal case of MPNST in the nasal cavity has been reported. Here, we report the case of a 4-day-old female newborn who presented with a nasal mass that re-enlarged after surgery and was diagnosed as MPNST of the nasal cavity on the basis of pathological results. This is the first report of MPNST in the nasal cavity of a neonate. Differential diagnosis and treatment of nasal masses have been proposed in the related literature.

FOXM1 promotes neurofibromatosis type 1-associated malignant peripheral nerve sheath tumor progression in a NUF2-dependent manner

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive soft-tissue sarcomas characterized by poor prognosis and low drug response rates. Traditional chemo/radiotherapies show only mild benefits for patients with MPNSTs, and no targeted therapy is available in the clinic. A better understanding of the molecular background of MPNSTs is critical for the development of effective targeted therapies. Forkhead box M1 (FOXM1) has been implicated in the progression of many human malignancies, though its role in MPNSTs is unclear. In this study, using four Gene Expression Omnibus (GEO) datasets and a tissue microarray, we demonstrated that FOXM1 upregulation was associated with poor prognosis in patients with MPNSTs. FOXM1 overexpression and knockdown regulated the proliferation and colony formation of MPNST cells. Using bioinformatics analysis and luciferase reporter assays, we identified NUF2 as a direct downstream target of FOXM1. Both in vitro and in vivo experiments demonstrated that the induction of MPNST cell proliferation by FOXM1 was dependent on elevated NUF2 expression, as NUF2 knockdown abolished the FOXM1-induced proliferation of MPNST cells. Our study showed that the FOXM1-NUF2 axis mediates human MPNST progression and could be a potential therapeutic target.

Atypical neurofibromas reveal distinct epigenetic features with proximity to benign peripheral nerve sheath tumor entities

BACKGROUND

Plexiform neurofibromas can transform into atypical neurofibromas (ANF) and then further progress to aggressive malignant peripheral nerve sheath tumors (MPNST). ANF have been described to harbor distinct histological features and frequent loss of CDKN2A/B. However, histological evaluation may be rater-dependent, and detailed knowledge about the molecular mechanisms of malignant transformation is scarce. In general, malignant transformation can be accompanied by significant epigenetic changes, and global DNA methylation profiling is able to differentiate relevant tumor subgroups. Therefore, epigenetic profiling might provide a valuable tool to distinguish and characterize ANF with differing extent of histopathological atypia from neurofibromas and MPNST.

METHODS

We investigated 40 tumors histologically diagnosed as ANF and compared their global methylation profile to other peripheral nerve sheath tumors.

RESULTS

Unsupervised class discovery and t-SNE analysis indicated that 36/40 ANF cluster with benign peripheral nerve sheath tumors with clear separation from MPNST. 21 ANF formed a molecularly distinct cluster in proximity to schwannomas. Tumors in this cluster had a frequent heterozygous or homozygous loss of CDKN2A/B and significantly more lymphocyte infiltration than MPNST, schwannomas, and NF. Few ANF clustered closely with neurofibromas, schwannomas, or MPNST, raising the question, whether diagnosis based on histological features alone might pose a risk to both over- and underestimate the aggressiveness of these lesions.

CONCLUSIONS

Our data suggest that ANF with varying histological morphology show distinct epigenetic similarities and cluster in proximity to benign peripheral nerve sheath tumor entities. Future investigations should pay special respect to correlating this methylation pattern to clinical outcomes.

Extraneural Sclerosing Perineurioma of the Tongue

Perineurioma (PN) is an uncommon benign peripheral nerve sheath tumor. For the rarity of this tumor in the oral cavity, otolaryngologists and oral surgeons might not be familiar with this entity. Perineuriomas are typically benign and complete excision is deemed adequate management. Thus, their histological recognition is mandatory to avoid unnecessary overtreatment. We report the clinicopathologic findings of an uncommon variant, the Extraneural Sclerosing PN, in an unusual and never described site, the tongue.

Hybrid Neurofibroma/Schwannoma of the Oral Cavity: A Rare Case Report and Literature Review

Hybrid peripheral nerve sheath tumors show combined features of more than one type of conventional benign peripheral nerve sheath tumors. There are few cases reported of hybrid peripheral nerve sheath tumors in the head and neck region. A 68-year-old female patient was referred for evaluation of an oral swelling lasting five years. Intraoral examination revealed a small mobile nodule located in the lower vestibule. The patient underwent excisional biopsy and microscopic evaluation showed typical features of neurofibroma enclosing areas with palisading nuclei compatible with Antoni A pattern, which are seen in schwannomas. These regions showed strong and diffuse immunoreactivity for S100 protein and moderate positivity in the neurofibroma area. CD34 was positive in the neurofibroma area and entrapped axons were positive for neurofilament. The final diagnosis was oral hybrid neurofibroma-schwannoma tumor. Hybrid peripheral nerve sheath tumors, although extremely rare, may arise within the oral cavity. To the best of our knowledge, this is the first neurofibroma-schwannoma tumor reported in the oral cavity. Recognizing hybrid peripheral nerve sheath tumors as a distinct clinicopathological entity is important because they may also be associated with syndromic disorders.

Advancements in therapeutic approaches for malignant peripheral nerve sheath tumor

Tweetable abstract Emerging targeted therapies offer hope for malignant peripheral nerve sheath tumor. Innovative drug delivery enhances potential treatments. #MPNST #TargetedTherapies #TherapeuticDelivery.

Multiplatform molecular profiling uncovers two subgroups of malignant peripheral nerve sheath tumors with distinct therapeutic vulnerabilities

Malignant peripheral nerve sheath tumor (MPNST) is a highly aggressive sarcoma, and a lethal neurofibromatosis type 1-related malignancy, with little progress made on treatment strategies. Here, we apply a multiplatform integrated molecular analysis on 108 tumors spanning the spectrum of peripheral nerve sheath tumors to identify candidate drivers of MPNST that can serve as therapeutic targets. Unsupervised analyses of methylome and transcriptome profiles identify two distinct subgroups of MPNSTs with unique targetable oncogenic programs. We establish two subgroups of MPNSTs: SHH pathway activation in MPNST-G1 and WNT/ß-catenin/CCND1 pathway activation in MPNST-G2. Single nuclei RNA sequencing characterizes the complex cellular architecture and demonstrate that malignant cells from MPNST-G1 and MPNST-G2 have neural crest-like and Schwann cell precursor-like cell characteristics, respectively. Further, in pre-clinical models of MPNST we confirm that inhibiting SHH pathway in MPNST-G1 prevent growth and malignant progression, providing the rational for investigating these treatments in clinical trials.

Solitary Malignant Peripheral Nerve Sheath Tumor of Lumbar Vertebra Mimicking Metastatic Malignancy

ABSTRACT

Malignant peripheral nerve sheath tumor involving solitary lumbar vertebra is extremely rare. A 72-year-old man had a chief complaint of growing lumbocrural pain for 2 months. The CT scan detected a solitary vertebral lesion, which highly supported the diagnosis of metastatic malignancy. 18 F-FDG PET/CT demonstrated that the vertebral lesion had heterogeneous intense FDG accumulation with an SUV max of 16.4. The pathological examination confirmed the diagnosis of malignant peripheral nerve sheath tumor. This case highlights that MPNST should be considered when there is solitary vertebra invasion with increased FDG uptake.

Patient demographics, tumor characteristics, and outcomes following surgical treatment of benign and malignant brachial plexus tumors: a systematic review

BACKGROUND

Various treatment options have been introduced for the management of primary tumors of the brachial plexus (BP), ranging from conservative therapy to wide local excision with/without postoperative chemoradiotherapy. However, no consensus exists regarding optimal treatment strategies based on collated and published data.

OBJECTIVE

The aim of this study was to investigate the clinicopathological characteristics and outcome of patients with primary tumors of the BP who underwent surgical treatment.

DATA SOURCES

A systematic search of the four main online databases, including Web of Science (WOS), PubMed, Scopus, and Google Scholar, was conducted.

STUDY SELECTION

All related articles addressing the clinical outcome and role of surgical interventions for management of primary tumors of the BP.

INTERVENTION

Optimal surgical and radiotherapeutic interventions for benign and malignant lesions based on the pathologic characteristics and location of primary BP tumors.

RESULTS

A total of 687 patients (693 tumors) with a mean age of 41.7±8.7 years old were evaluated. In total, 629 (90.8%) tumors were benign, and 64 (9.2%) were malignant, with a mean tumor size of 5.4±3.1 cm. The location of the tumor was reported for 639 patients. For these tumors, 444 (69.5%) originated from the supraclavicular region, and 195 (30.5%) were infraclavicular. The trunks were the most common location for tumor involvement, followed by the roots, cords, and terminal branches. Gross total resection was achieved in 432 patients and subtotal resection (STR) was performed in 109 patients. With neurofibromas, STR still resulted in good outcomes. The outcomes following treatment of malignant peripheral nerve sheath tumors were poor regardless of the type of resection. In general, symptoms related to pain and sensory issues resolved rapidly postoperatively. However, the resolution of motor deficits was often incomplete. Local tumor recurrence occurred in 15 (2.2%), patients and distant metastasis was observed in only eight (1.2%) cases. The overall mortality was 21 (3.1%) patients among the study population.

LIMITATIONS

The main limitation was the lack of level I and II evidence.

CONCLUSIONS

The ideal management strategy for primary BP tumors is complete surgical resection. However, in some cases, particularly for neurofibromas, STR may be preferable to preserve maximal neurological function. The degree of surgical excision (total or subtotal) mainly depends on the pathological characteristics and primary location of the tumor.

Analysis of Survival Differences Between Cutaneous and Subcutaneous Malignant Peripheral Nerve Sheath Tumors

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNSTs) are clinically aggressive soft tissue sarcomas that can present as cutaneous or subcutaneous based tumors that are commonly associated with neurofibromatosis type 1. Historically, these tumors have poor outcomes. Previously, no study has compared survival of cutaneous versus subcutaneous MPNSTs.

OBJECTIVE

This study aims to investigate the difference in overall survival (OS) among cutaneous MPNSTs, subcutaneous MPNSTs of the head and neck, and subcutaneous MPNSTs of the trunk and extremities.

MATERIALS AND METHODS

Nine hundred eighteen patients were included in this retrospective study using the Surveillance, Epidemiology, and End-Results (SEER-9) database with primary cutaneous or subcutaneous MPNSTs from 1975 to 2016. OS was calculated using cox proportional hazard models for each group.

RESULTS

No significant difference was revealed in OS between cutaneous or subcutaneous MPNSTs, regardless of location. Factors associated with decreased OS included advanced age, higher grade, and nondefinitive surgical modality.

CONCLUSION

This study results implies that unlike other soft tissue sarcomas, cutaneous presentation does not improve OS in patients with MPNSTs compared with their subcutaneous counterparts.

Schwannoma of the colon: a rare submucosal neoplasm

Schwannomas are nerve sheath tumours that can be found throughout the body along peripheral nerves. Primary schwannomas of the colon are very rare. They are usually benign and their surgical resection is considered curative. They are, however, difficult to diagnose preoperatively and therefore tend to be overtreated with major colorectal surgery.

Giant lumbar schwannoma with retroperitoneal extension and vertebral body invasion: a case report

Schwannoma is a type of peripheral nerve sheath tumor derived from Schwann cells. There have been only a few cases of giant lumbar schwannoma with retroperitoneal extension eroding the vertebral body documented. Thus, managing these tumors presents various challenges. This paper reports a case of a 59-year-old woman who experienced lower back radicular pain for a year. A lumbar magnetic resonance imaging revealed the presence of a giant extradural soft tissue tumor measuring 8.6x7.4x9.7 cm, compressing the right L5-S1 neural foramen and extending into the retroperitoneal space while eroding the L5 vertebral body. The patient underwent surgery via a retroperitoneal approach, and the tumor was successfully resected. Histopathological examination confirmed the diagnosis of schwannoma. In conclusion, giant retroperitoneal lumbar schwannomas with bone invasion are rare, and gross total resection is the preferred treatment option, but the size and location of the tumor can make the surgery challenging.

LPAR1 and aberrantly expressed LPAR3 differentially promote the migration and proliferation of malignant peripheral nerve sheath tumor cells

Schwann cell-derived neoplasms known as malignant peripheral nerve sheath tumors (MPNSTs) are the most common malignancy and the leading cause of death in individuals with neurofibromatosis Type 1. Using genome-scale shRNA screens, we have previously found evidence suggesting that lysophosphatidic acid receptors (LPARs) are essential for MPNST proliferation and/or survival. Here, we examine the expression and mutational status of all six LPA receptors in MPNSTs, assess the role that individual LPA receptors play in MPNST physiology and examine their ability to activate key neurofibromin-regulated signaling cascades. We found that human Schwann cells express LPAR1 and LPAR6, while MPNST cells express predominantly LPAR1 and LPAR3. Whole exome sequencing of 16 MPNST cell lines showed no evidence of mutations in any LPAR genes or ENPP2, a gene encoding a major LPA biosynthetic enzyme. Oleoyl-LPA, an LPA variant with an unsaturated side chain, promoted MPNST cell proliferation and migration. LPAR1 knockdown ablated the promigratory effect of LPA, while LPAR3 knockdown decreased proliferation. Inhibition of R-Ras signaling with a doxycycline-inducible dominant negative (DN) R-Ras mutant, which inhibits both R-Ras and R-Ras2, blocked LPA's promigratory effect. In contrast, DN R-Ras did not affect migration induced by neuregulin-1β (NRG1β), suggesting that LPA and NRG1β promote MPNST migration via distinct pathways. LPA-induced migration was also inhibited by Y27632, an inhibitor of the ROCK1/2 kinases that mediate R-Ras effects in MPNSTs. Thus, LPAR1 and aberrantly expressed LPAR3 mediate distinct effects in MPNSTs. These receptors and the signaling pathways that they regulate are potentially useful therapeutic targets in MPNSTs.