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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. [ABSTRACT FROM AUTHOR]

ObjectivePeripheral nerve sheath tumors (PNST) include mainly schwannomas and neurofibromas. Surgical resection represents the mainstay of treatment but due to their pathogenesis, distinguishing between intact functional nerve and the fibers from whence the PNST arose may not always be easy to perform, constituting the most relevant risk factor in determining a worsening in neurological condition. The introduction of intraoperative tools to better visualize these tumors could help achieve a gross-total resection. In this study, we analyzed the effect of sodium fluorescein (SF) on the visualization and resection of a large cohort of PNST.MethodsBetween September 2018 and December 2021, 142 consecutive patients harboring a suspected PNST underwent fluorescein-guided surgery at the Department of Neurosurgery of the Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy. All patients presented with a different degree of contrast enhancement at preoperative MRI. SF was intravenously injected after intubation at 1 mg/kg. Intraoperative fluorescein characteristics and postoperative neurological and radiological outcomes were collected, analyzed, and retrospectively compared with a historical series.Results142 patients were included (42 syndromic and 100 sporadic); schwannoma was the predominant histology, followed by neurofibroma (17 neurofibroma e 12 plexiform neurofibroma) and MPNST. Bright fluorescence was present in all cases of schwannomas and neurofibromas, although with a less homogeneous pattern, whereas it was significantly less evident for malignant PNST; perineurioma and hybrid nerve sheath tumors were characterized by a faint fluorescence enhancement. The surgical resection rate in the general population and even among the subgroups was about 66.7%; from the comparative analysis, we found a consistently higher rate of complete tumor removal in plexiform neurofibromas, 66% in the “fluorescent” group vs 44% in the “historical” group (p-value < 0.05). The rate of complications and mean surgical time were superimposable among the two populations.ConclusionsSF is a valuable method for safe fluorescence-guided PNST and mimicking lesions resection. Our data showed a positive effect of fluorescein-guided surgery in increasing the rate of surgical resection of plexiform neurofibromas, suggesting a possible role in improving the functional and oncological outcome of these lesions.

Simple Summary: The peripheral nerve sheath tumors are relatively common neoplasms, belong to the soft tissue sarcomas group, and are poorly investigated in veterinary medicine; the diagnosis is complex, and therapeutic options are limited. The platelet-derived growth factor receptors, namely the β subunit, are an important class of tyrosine kinase receptors that can be activated by genetic alterations and contribute to the process of carcinogenesis, so the inhibition of this receptor is an important therapeutic target. Using the immunohistochemical technique, this study aims to evaluate the expression of this receptor in 19 samples, 10 malignant and 9 benign tumors. The results showed that the majority of benign tumors, about 67% of cases, expressed the receptor in less than 25% of neoplastic cells and, in 80% cases of malignant tumors, the receptor was expressed in more than 25% of neoplastic cells. It was also found that, in the larger tumors, the expression of this receptor was significantly higher. With these findings it seems reasonable to speculate that the drugs able to inhibit this receptor, such as toceranib, may be considered in the therapeutic approach of these tumors. As in humans, the prevalence of tumors in companion animals is increasing dramatically and there is a strong need for research on new pharmacological agents particularly for the treatment of those tumors that are resistant to conventional chemotherapy agents such as soft tissue sarcomas (STS). Because malignant (MPNST) and benign peripheral nerve sheath tumors (BPNST) are relatively common STS in dogs, the aim of this retrospective study was to evaluate the immunohistochemical (IHC) expression of PDGFR-β, contributing to its characterization as a potential target for their treatment. A total of 19 samples were included, 9 histologically classified as benign and the other 10 as malignant. The results showed diffuse immunoexpression in the cytoplasm of neoplastic cells. Six (66.7%) BPNST expressed the receptor in less than 25% of neoplastic cells and only three (33.3%) exhibited labelling in more than 25% of neoplastic cells. In contrast, all MPNST expressed PDGFR-β, and in 8 (80%) of these samples, the receptor was expressed in more than 25% of neoplastic cells, and only 2 (20%) cases expressed the receptor in less than 25% of neoplastic cells. PDGFR-β expression was significantly higher in MPNST and larger tumors, suggesting that drugs able to inhibit the activity of this tyrosine kinase receptor, such as toceranib, may be considered in the approach of unresectable tumors and/or in the context of adjuvant or neoadjuvant therapies. [ABSTRACT FROM AUTHOR]

Hybrid nerve sheath tumours (HNSTs) are benign tumours showing combined features of more than one peripheral nerve sheath tumour (PNST) entities. Most literature highlight combination of two entities. Only few reported cases involve all three components of PNST. Herein, we report a case of 33-year-old Malay lady, with left proximal middle finger soft tissue swelling for three months. Microscopically, the tumour is well-circumscribed, containing all three components of PNST, with each displaying its typical morphology and immunohistochemical staining pattern. This case suggests that PNSTs may be more closely related than what was earlier believed. However, whether HNSTs are part of the PNSTs spectrum with tumour syndromes association or a distinct entity is still a continuous debate. We also highlight the possibilities of recurrence and risk of malignant transformation in HNSTs. The exact pathogenesis, potential for recurrence and malignant transformation criteria for HNSTs are still vague due to their extreme rarity. [ABSTRACT FROM AUTHOR]

As in humans, the prevalence of tumors in companion animals is increasing dramatically and there is a strong need for research on new pharmacological agents particularly for the treatment of those tumors that are resistant to conventional chemotherapy agents such as soft tissue sarcomas (STS). Because malignant (MPNST) and benign peripheral nerve sheath tumors (BPNST) are relatively common STS in dogs, the aim of this retrospective study was to evaluate the immunohistochemical (IHC) expression of PDGFR-β, contributing to its characterization as a potential target for their treatment. A total of 19 samples were included, 9 histologically classified as benign and the other 10 as malignant. The results showed diffuse immunoexpression in the cytoplasm of neoplastic cells. Six (66.7%) BPNST expressed the receptor in less than 25% of neoplastic cells and only three (33.3%) exhibited labelling in more than 25% of neoplastic cells. In contrast, all MPNST expressed PDGFR-β, and in 8 (80%) of these samples, the receptor was expressed in more than 25% of neoplastic cells, and only 2 (20%) cases expressed the receptor in less than 25% of neoplastic cells. PDGFR-β expression was significantly higher in MPNST and larger tumors, suggesting that drugs able to inhibit the activity of this tyrosine kinase receptor, such as toceranib, may be considered in the approach of unresectable tumors and/or in the context of adjuvant or neoadjuvant therapies.

Fluorescence, fluorescein, CNS tumors, gliomas, PNST, 5-ALA, ICG, confocal endomicroscopy They found a dense and homogenous fluorescence in all extramedullary tumors and in 73.3% of intramedullary tumors, while 13.3% of intramedullary tumors presented lower and more heterogeneous fluorescence. Keywords: CNS tumors; gliomas; PNST; fluorescence; 5-ALA; fluorescein; ICG; confocal endomicroscopy EN CNS tumors gliomas PNST fluorescence 5-ALA fluorescein ICG confocal endomicroscopy 1 3 3 02/10/22 20220207 NES 220207 This Research Topic " I Intraoperative Fluorescence Imaging and Diagnosis in Central and Peripheral Nervous System Tumors: Established Applications and Future Perspectives i " consists of 13 articles contributed by 100 authors in the field of Neurosurgery, Neuropathology, Neuro-oncology, Medical Physics, and Biophotonics. [Extracted from the article]

The aim of this study was to re-evaluate archived samples of canine soft tissue sarcomas (STSs) morphologically consistent with peripheral nerve sheath tumors (PNSTs). In each case, an immunohistochemical panel was applied, including α-SMA, calponin, desmin, S-100, GFAP, NSE and Olig2, in order to assess whether the phenotype was consistent with the tumor histological appearance. Additionally, the expression of EGFR, a marker with potential therapeutic implications in malignant PNSTs, was evaluated. Twenty-one tumors were included. Fourteen cases (66.7%) were positive for one or more muscular markers and were reclassified as perivascular tumors (PWTs). A positive labeling for S-100 was observed in one tumor (4.8%), thus classifi ed as PNST. The other 6 tumors were generically classified as poorly differentiated STSs. No unique histopathological feature was observed within the three groups. NSE and Olig2 labeling was aspecific and not useful for diagnostic purposes. GFAP was negative in all cases. Six cases (28.6%) were positive for EGFR, including the PNST. Even after the application of a wide immunohistochemical panel, distinguishing between PNSTs and PWTs remains a challenge. Finally, a subgroup of cases cannot be classified based on light microscopy alone.

Objectives: To retrospectively evaluate the diagnostic performance of morphological signs observed on conventional magnetic resonance (MR) imaging to differentiate benign from malignant peripheral solid tumors of soft tissue with myxoid stroma.Methods: MR images from 95 consecutive histopathologically proven tumors (26 benign and 69 malignant) of soft tissues with myxoid components were evaluated in our tertiary referral center. Two radiologists, blind to pathology results, independently reviewed conventional MR sequences including at least a) one T2-weighted sequence with or without fat suppression; b) one T1-weighted sequence without fat suppression; and c) one T1-weighted sequence with gadolinium-complex contrast enhancement and fat suppression. Multiple criteria were defined to analyze morphology, margins, architecture and tumor periphery and evaluated for each lesion. Intra- and inter-observer reproducibility and Odds ratios were calculated for each criterion.Results: The most relevant and reproducible criteria to significantly predict malignancy were: (1) ill-defined tumor margins, (2) a hemorrhagic component, (3) intra-tumoral fat, (4) fibrosis and (5) the "tail sign". A lesion is classified as malignant if any of these 5 criteria is present, and benign if none of them are observed. Therefore, this combination provides a sensitivity of 92.9% and a specificity of 93.3%.Conclusion: Conventional MR imaging provides reproducible criteria that can be combined to differentiate between benign and malignant solid tumors of soft tissue with myxoid stroma. [ABSTRACT FROM AUTHOR]

An adult Goldfish (Carassius auratus) developed an exophitic, multinodular, mass in the dorsal region involving the fin. The clinical and pathologic approach included ultrasonography, cytology, histopathology, immunohistochemistry, and ultrastructural evaluation. B-mode and color Doppler ultrasonographic findings showed an oval, well-defined mass with slightly inhomogeneous parenchymatous echotexture associated with an intense intralesional vascularization. Cytology and histology revealed neoplastic pleomorphic spindle cells arranged in a storiform pattern or in palisades typical of Antoni A pattern schwannoma. Moderate anisocytosis and anisokaryosis and occasional binucleation were also present. The neoplastic tissue deeply infiltrated the skeletal muscle of the dorsal region. Immunohistochemistry showed a diffuse cytoplasmic immunoreactivity of neoplastic cells to S100 protein and proliferating cell nuclear antigen (PCNA); glial fibrillary acidic protein was negative. The PCNA proliferation rate was 23.5% (calculated as the mean of 10 fields). Ultrastructurally, neoplastic cells were juxtaposed with parallel nuclei forming the typical palisade pattern and sharing cytoplasmic and nuclear features with human schwannoma. This is the first cytologic description supplied with echographic investigation of a malignant schwannoma in a fish species. [ABSTRACT FROM AUTHOR]

Objective Peripheral nerve sheath tumors (PNSTs) are tumors arising from the neural sheath cells. Surgery plays a central role in the management of this disease, with the purpose of obtaining radical tumor's resection and at the same time providing the best outcome. We retrospectively analyzed 53 PNSTs in 42 patients in an attempt to identify some factors that may improve surgical outcome. Material and Methods Clinical, histologic, and imaging data of 42 patients with PNSTs treated at our Institute between 2001 and 2012 were collected and analyzed. We evaluated the outcome 1 month and 6 month after surgery using three clinical parameters (pain, motor deficits, and sensory deficits) in relation to different histotypes, the presence of neurofibromatosis type 1, tumor location, and duration of symptoms before treatment. Results The best functional results were observed in patients having neurofibromas; the worst outcomes were observed in patients with malignant PNSTs. The other factors were not associated with outcome. Conclusion The timing of surgery is the most important predictive factor of surgical outcome, being the only factor that allows to improve the outcome. With the current study, we want to stress the importance of treating PNSTs as soon as possible to provide the best outcome possible. [ABSTRACT FROM AUTHOR]

Summary: Currently canine fibrosarcomas and peripheral nerve sheath tumours (PNSTs) are differentiated by their histopathological phenotype. Preliminary global transcriptomic analysis has identified genes with significant differential expression in both tumour types that may act as potential tumour markers. The aim of the present study was to establish reverse transcriptase polymerase chain reaction (RT-PCR) assays for the differentiation of formalin-fixed and paraffin wax-embedded tumours of both types. Fifty histologically well-defined examples of canine fibrosarcomas and PNSTs were characterized immunohistochemically for the expression of S100, laminin and PGP 9.5. RT-PCR assays for the potential fibrosarcoma markers FHL2-Ex4 and FHL2-Ex9 and the PNST markers GLI1 and CLEC3B were established and tested for their specificity and sensitivity to differentiate fibrosarcomas and PNSTs by their mRNA expression. Immunohistochemical analysis challenged the value of S100, laminin and PGP 9.5 for the diagnosis of PNSTs, since both PNSTs and fibrosarcomas showed similar expression of these proteins. In contrast, a combination of the markers GLI1 and CLEC3B differentiated PNSTs from fibrosarcomas with a sensitivity of 89% and a specificity of 87%. The proposed fibrosarcoma markers FHL2-Ex4 and FHL2-Ex9 failed to separate PNSTs and fibrosarcomas (sensitivity 50%, specificity 88%). The failure of these markers to unequivocally separate fibrosarcomas and PNSTs raises questions as to whether histologically uniform PNSTs are less uniform at the molecular level than expected or if both tumour types, despite their different morphology, are more closely related in terms of their histogenesis than previously thought. [ABSTRACT FROM AUTHOR]

Background: The objective of this study was to evaluate the effect on outcomes of intraoperative recombinant human interleukin-2 injection after surgical resection of peripheral nerve sheath tumours. In this double-blind trial, 40 patients due to undergo surgical excision (<5 mm margins) of presumed peripheral nerve sheath tumours were randomized to receive intraoperative injection of interleukin-2 or placebo into the wound bed. Results: There were no significant differences in any variable investigated or in median survival between the two groups. The median recurrence free interval was 874 days (range 48-2141 days), The recurrence-free interval and overall survival time were significantly longer in dogs that undergone the primary surgery by a specialist-certified surgeon compared to a referring veterinarian regardless of whether additional adjunct therapy was given. Conclusion: Overall, marginal excision of peripheral nerve sheath tumours in dogs resulted in a long survival time, but adjuvant treatment with recombinant human interleukin-2 (rhIL-2) did not provide a survival advantage. [ABSTRACT FROM AUTHOR]

The frequency and morphological spectrum of gastrointestinal peripheral nerve sheath tumors (PNSTs) from consecutive case material has not been studied in the c-KIT era. We reviewed all mesenchymal gastrointestinal (GI) lesions at our departments according to current diagnostic criteria. PNSTs formed the third commonest group of mesenchymal GI tumors with a lower frequency (< or =5%) compared to gastrointestinal stromal tumors (GISTs; approximately 50%) and smooth muscle neoplasms ( approximately 30%). Granular cell tumors (GCTs; n = 31) and schwannomas (n = 22) were the most common types of PNSTs encountered. Rare tumors included neurofibromatosis 1 (NF1)-associated PNSTs (n = 5) and gastric perineurioma (n = 1). Thirteen schwannomas (including also some recent cases) were initially diagnosed as GIST, leiomyoma, or neurofibroma. Unusual histological variants included sigmoid GCT with prominent lipomatous component (n = 1), reticular-microcystic schwannoma of small (n = 1) and large (n = 1) bowel, NF1-associated gastric schwannoma (the first case to date), and psammomatous melanotic colonic schwannoma unrelated to Carney complex (n = 1). PNSTs coexisted with GIST in four patients (three had definite NF1). In conclusion, PNSTs of the GI tract are rare uniformly benign neoplasms that may show schwannian, perineurial, fibroblastic, or mixed differentiation. Most of them (92%) occurred sporadically unassociated with NF1 or NF2. Gastrointestinal PNSTs are still underrecognized by general pathologists. Awareness of their diverse morphology will help to avoid confusing them with smooth muscle neoplasms and GIST that they may closely mimic. [ABSTRACT FROM AUTHOR]

Background and methods: 44 peripheral nerve sheath tumors (PNST) (27 schwannomas, 9 neurofibromas and 8 malignant peripheral nerve sheath tumors (MPNST)) were analyzed to determine DNA ploidy pattern and to clarify the conflicting data in the literature concerning this topic (whether benign PNSTs are aneuploid or not). For further insight we analyzed 6 schwannomas, one atypical neurofibroma and five MPNSTs by fluorescence in situ hybridization (FISH) technique using centromeric chromosome probes (7, 17 and 18) and automatic image analysis station, Metafer 4. Results: Benign schwannomas (including the problematic variants as ancient, cellular, neuroblastoma like and multiplex schwannomas) could be characterized by euploid‐polyploidisation and by their 4c peak height value which was usually more than 10% of total cell number measured. These characters were not found among neurofibromas and MPNST‐s. FISH analysis revealed and confirmed that the ‘normal’ euploid–polyploid cells are mainly eusomic–polysomic containing two, four, eight or sixteen signals for each chromosomes examined, but in a small proportion aneusomy was found among tumor cells of benign schwannomas (average: 2.58; range 1.33–3.44). In contrast, the atypical neurofibroma displayed marked aneusomy (18.44%) but it contained normal eusomic and polysomic cells too. Two diploid MPNSTs proved to be clearly aneusomic with trisomy of chromosome 17 and monosomy of chromosome 18. Conclusions: All these data suggest that ploidy pattern determination combined with FISH analysis may be a very useful supplementary tool for making a right diagnosis (to differentiate benign versus malignant schwannomas in problematic variants) and to understand better the malignant transformation in PNSTs. [ABSTRACT FROM AUTHOR]

Peripheral nerve sheath tumors (PNSTs) include schwannomas, neurofibromas (NFs), and plexiform neurofibromas (PNFs), among others. While they are benign tumors, according to their biological behavior, some have the potential for malignant degeneration, mainly PNFs. The specific factors contributing to the more aggressive behavior of some PNSTs compared to others are not precisely known. Considering that lipid homeostasis plays a crucial role in fibrotic/inflammatory processes and in several cancers, we hypothesized that the lipid asset was also unbalanced in this group of nerve tumors. Through untargeted lipidomics, NFs presented a significant increase in ceramide, phosphatidylcholine, and Vitamin A ester. PNFs displayed a marked decrease in 34 out of 50 lipid class analyzed. An increased level of ether- and oxidized-triacylglycerols was observed; phosphatidylcholines were reduced. After sphingolipidomic analysis, we observed six sphingolipid classes. Ceramide and dihydroceramides were statistically increased in NFs. All the glycosylated species appeared reduced in NFs, but increased in PNFs. Our findings suggested that different subtypes of PNSTs presented a specific modulation in the lipidic profile. The untargeted and targeted lipidomic approaches, which were not applied until now, contribute to better clarifying bioactive lipid roles in PNS natural history to highlight disease molecular features and pathogenesis. [ABSTRACT FROM AUTHOR]

Introduction: In this case report we present the rare case of a distally located peripheral nerve sheath tumor (PNST) of the left ulnar nerve in a two-year-old female Rottweiler dog. We discuss the clinical and diagnostic findings and the challenges of the diagnosis. The dog was successfully treated with a limb sparing partial neurectomy. After surgery, the dog did not show any pain or lameness on long term follow-up.

Background: Surgery for peripheral nerve sheath tumors aims to preserve functional fascicles achieving gross-total resection. Increasing the visualization of anatomic details helps to identify the different layers and the tumor-nerve interface. The traditional microscope can present some limitations in this type of surgery, such as its physical obstruction., Objective: To present a proof-of-concept study about exoscope-guided surgery for schwannomas of the lower limbs, to analyze the advantages and disadvantages of the 4K, high-quality, 3-dimensional (3D) imaging., Methods: We analyzed 2 consecutive surgical cases of suspected schwannomas of the lower limbs using the ORBEYE™ exoscope (Olympus). A standard operative microscope was also available in the operating room. All procedures were performed with neurophysiological monitoring, to identify functioning nerves and to localize the tumor capsule safest entry point. The cases are reported according to the PROCESS guidelines., Results: In both cases, we achieved a gross total resection of the schwannomas; the exoscope provided an excellent view of the anatomic details at tumor-nerve interface, as visible in intraoperative images and in the 3D-4K video supporting these findings. The surgeon's position was comfortable in both cases, although if the co-surgeon positioned himself in front of the first surgeon, the comfort was slightly reduced. The 4K monitor allowed a realistic, nontiring 3D vision for all the team., Conclusion: The ORBEYETM, after an adequate learning curve, can represent a feasible and comfortable instrument for nerve tumor surgery, which is usually performed in a single horizontal plane. Further and wider clinical series are necessary to confirm this first impression., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Objective: Spinal peripheral nerve sheath tumors (PNSTs) are a group of rare tumors originating from the nerve and its supporting structures. Standard surgical management typically entails laminectomy with or without facetectomy to gain adequate tumor exposure. Arthrodesis is occasionally performed to maintain spinal stability and mitigate the risk of postoperative deformity, pain, or neurological deficit. However, the factors associated with the need for instrumentation in addition to PNST resection in the same setting remain unclear., Methods: An institutional tumor registry at a tertiary care center was queried for patients treated surgically for a primary diagnosis of spinal PNST between 2002 and 2016. An analysis focused on patients in whom a facetectomy was performed during the resection. The addition of arthrodesis at the index procedure comprised the primary outcome. The authors also recorded baseline demographics, tumor characteristics, and surgery-related variables. Logistic regression was used to identify factors associated with increased risk of fusion surgery., Results: A total of 163 patients were identified, of which 56 (32 had facetectomy with fusion, 24 had facetectomy alone) were analyzed. The median age was 48 years, and 50% of the cohort was female. Age, sex, and race, as well as tumor histology and size, were evenly distributed between patients who received facetectomy alone and those who had facetectomy and fusion. On univariate analysis, total versus subtotal facetectomy (OR 9.0, 95% CI 2.01-64.2; p = 0.009) and cervicothoracic versus other spinal region (OR 9.0, 95% CI 1.51-172.9; p = 0.048) were significantly associated with increased odds of performing immediate fusion. On multivariable analysis, only the effect of total facetectomy remained statistically significant (OR 6.75, 95% CI 1.47-48.8; p = 0.025)., Conclusions: The authors found that total facetectomy and cervicothoracic involvement may be highly associated with the need for concomitant arthrodesis at the time of index surgery. These findings may help surgeons to determine the best surgical planning for patients with PNST.