Low-grade Neuroepithelial Tumors Research Articles

Low-grade glioma of the temporal lobe and tumor-related epilepsy in children.

Low-grade glioma is the most common brain tumor among children and adolescents. When these tumors arise in the temporal lobe, patients frequently present with seizures that are poorly controlled with antiepileptic drugs. Here we summarize the clinical features, pathophysiology, preoperative evaluation, surgical treatment, and outcomes of pediatric patients with low-grade gliomas in the temporal lobe. We reviewed the literature on pediatric low-grade gliomas in the temporal lobe, focusing on cohort studies and systematic reviews that described surgical treatment strategies and reported both oncologic and epilepsy outcomes. The differential diagnoses of pediatric low-grade gliomas in the temporal lobe include ganglioglioma, dysembryoplastic neuroepithelial tumor, desmoplastic infantile ganglioglioma, papillary glioneuronal tumor, pilocytic astrocytoma, pleomorphic xanthoastrocytoma, angiocentric glioma, and polymorphous low-grade neuroepithelial tumor of the young. There is no consensus on the optimal surgical approach for these tumors: lesionectomy alone, or extended lesionectomy with anterior temporal lobectomy, with or without removal of mesial temporal structures. Gross total resection and shorter preoperative duration of epilepsy are strongly associated with favorable seizure outcomes, defined as Engel Class I or Class II, approaching 90% in most series. The risk of surgical complications ranges from 4 to 17%, outweighing the lifetime risks of medically refractory epilepsy. Pediatric patients with temporal low-grade glioma and tumor-related epilepsy are best managed by a multidisciplinary epilepsy surgery team. Early and appropriate surgery leads to prolonged survival and a greater likelihood of seizure freedom, improving their overall quality of life.

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY): A case report with surgical and neuropathological differential diagnosis.

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a rare entity of low-grade neuroepithelial tumors that primarily affects children and young adults. This distinct type of tumor presents unique challenges in diagnosis and management. With its relatively recent identification, researchers and clinicians are striving to understand the characteristics, behavior, and optimal treatment strategies. The symptoms are primarily related to seizures. However, PLNTY can be asymptomatic in some cases. This is a single-center case report study and a literature review paper. We reviewed a case treated and diagnosed at the Ankara University Faculty of Medicine, Department of Neurosurgery. The demographic data, clinical follow-ups, laboratory, and radiological data of the patients were assessed. We present a 32-year-old male patient who has undergone gross total surgical excision with strict clinical follow-up. Clinical course as well as surgical data of the patient were observed and analyzed. On imaging, morphologic resembling and indistinctive clinical course can be nonspecific, contributing to diagnostic uncertainties. This case report was written with the notion that rare diagnoses present an opportunity to understand the progression and patho-oncological factors that can pave the way for better treatment.

Identification of Multiclass Pediatric Low-Grade Neuroepithelial Tumor Molecular Subtype with ADC MR Imaging and Machine Learning.

Molecular biomarker identification increasingly influences the treatment planning of pediatric low-grade neuroepithelial tumors (PLGNTs). We aimed to develop and validate a radiomics-based ADC signature predictive of the molecular status of PLGNTs. In this retrospective bi-institutional study, we searched the PACS for baseline brain MRIs from children with PLGNTs. Semiautomated tumor segmentation on ADC maps was performed using the semiautomated level tracing effect tool with 3D Slicer. Clinical variables, including age, sex, and tumor location, were collected from chart review. The molecular status of tumors was derived from biopsy. Multiclass random forests were used to predict the molecular status and fine-tuned using a grid search on the validation sets. Models were evaluated using independent and unseen test sets based on the combined data, and the area under the receiver operating characteristic curve (AUC) was calculated for the prediction of 3 classes: KIAA1549-BRAF fusion, BRAF V600E mutation, and non-BRAF cohorts. Experiments were repeated 100 times using different random data splits and model initializations to ensure reproducible results. Two hundred ninety-nine children from the first institution and 23 children from the second institution were included (53.6% male; mean, age 8.01 years; 51.8% supratentorial; 52.2% with KIAA1549-BRAF fusion). For the 3-class prediction using radiomics features only, the average test AUC was 0.74 (95% CI, 0.73-0.75), and using clinical features only, the average test AUC was 0.67 (95% CI, 0.66-0.68). The combination of both radiomics and clinical features improved the AUC to 0.77 (95% CI, 0.75-0.77). The diagnostic performance of the per-class test AUC was higher in identifying KIAA1549-BRAF fusion tumors among the other subgroups (AUC = 0.81 for the combined radiomics and clinical features versus 0.75 and 0.74 for BRAF V600E mutation and non-BRAF, respectively). ADC values of tumor segmentations have differentiative signals that can be used for training machine learning classifiers for molecular biomarker identification of PLGNTs. ADC-based pretherapeutic differentiation of the BRAF status of PLGNTs has the potential to avoid invasive tumor biopsy and enable earlier initiation of targeted therapy.

Abstract 5137: BRAF mutations in primary central nervous system tumors

Abstract Background: BRAF alterations are present in a variety of primary central nervous system (CNS) tumors from 3% in glioblastomas to 60% in pleomorphic xanthoastrocytomas. BRAF V600E mutation is the most common BRAF alteration found in tumors and has been successfully targeted by combining BRAF/MEK inhibitors in different tumor types, including gliomas. We aimed to describe the clinical and genomic features of primary CNS tumors harboring BRAF alterations and real-world data on BRAF-targeted therapy including our experience sequencing BRAF-directed therapies (BDI) in gliomas. Methods: Single-center retrospective analysis of patients with diagnosis of primary CNS tumors with NGS testing. Clinical, histological and molecular characteristics were analyzed. Results: 44 patients with BRAF mutant primary CNS tumors were included, 28 (64%) were male. 24 (55%) had histology consistent with high-grade glioma (HGG), 14 (32%) low grade glioma (LGG), 4 (9%) low grade neuroepithelial tumors and 2 (4%) others. Missense mutations were found in 77%, followed by amplifications (9%), fusions (9%) and in/del alterations (5%). V600E was the most common mutation (63%), followed by class 2 (16%) and 3 (7%) mutations and amplifications (9%). Co-occurring mutations were found in CDKN2A/B (22), TERT (20) and MTAP (12), median TMB was 2 mut/mb and only 2 patients had high TMB. 4 patients had commuted IDH1 (3 R132H), non-concurring with a V600E mutation. For patients with HGG, median age at diagnosis was 47 years and 16 (66%) were male. Lesions were more frequent in left hemisphere (70%) and temporal lobe (54%). V600E was found in 50% of cases, KIAA1549-BRAF fusion was found in 1 case. Median follow-up was 40 months (95% CI 11-68) and median overall survival (OS) was 22 months (3.4-40) for the whole population, and 56 (4-109) months for patients treated with BDI (n=4). All 4 patients had an OS >30 months. In the LGG cohort, median age at diagnosis was 34 years (IQR 24-46), 8 (57%) were male. 50% of the lesions were in the left side and 21% of the tumors were in the posterior fossa. 78% had a V600E mutation, with no statistical difference with HGG cohort (p=.082). Median follow up was 11 months, median OS was not reached. For 5 patients treated at recurrence with BDI, median PFS was 15 months (3-27).5 patients were treated with plixorafenib (PLX8394) on clinical trial achieving disease control (PR +SD) in 4 cases. Upon progression, 4 were rechallenged with dabrafenib + trametinib and 1 with another BDI. 4 patients had a partial response with duration of response >6 months in 3 cases. Conclusion: BRAF mutant CNS tumors are a heterogeneous disease. Longer survival was observed in the small group of HGG patients treated with BDI compared to SoC (56 months vs 22months). BDI rechallenge showed durable responses in heavily pretreated patients. Further molecular characterization of these patients is ongoing. The best therapeutical sequencing strategy for BDI remains uncertain. Citation Format: Juan B. Blaquier, Fulvio D'Angelo, Dalissa Tejera, Ruham A. Nasany, Gaurav Saigal, Antonio Iavarone, Macarena I. de la Fuente. BRAF mutations in primary central nervous system tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5137.

Clinicopathological analysis of rosette-forming glioneuronal tumors

BackgroundThis study aimed to investigate the clinicopathological characteristics, diagnostic indicators, and critical factors for the differential diagnosis of rosette-forming glioneuronal tumor (RGNT).Patients and methodsThis retrospective study included six surgically treated RGNT cases. We analyzed and summarized their clinical manifestations, radiological features, histological morphology, immunophenotype, and molecular genetic changes, supplemented with a literature review.ResultsThe patients comprised four males and two females with a mean age of 35 years. The tumors were located in the cerebellum (two cases); the fourth ventricle, quadrigeminal cistern, and third ventricle (one case each); and the fourth ventricle and brainstem (one case). Clinical manifestations included headaches in four cases, left eyelid ptosis in one case, and one asymptomatic case only identified during physical examination. Microscopically, the tumor cells were uniform in size and were marked by rosette-like or pseudorosette-like structures around the neuropil and blood vessels. Immunohistochemistry revealed biphasic patterns. The central neuropil components of the rosette-like structures around the neuropil and the pseudorosette structures of the perivascular regions expressed Syn, while the cells surrounding the rosettes expressed Olig2 and not GFAP. GFAP and S-100 were expressed in the glial components but not in the rosette or pseudorosette regions. The Ki-67 proliferation index was typically low. Molecular genetic analysis showed that the main molecular changes involved FGFR1 mutation accompanied by PIK3R1 mutation. None of the patients received chemoradiotherapy postoperatively. Follow-up durations varied between 4 and 23 months with no recorded recurrence or metastasis.ConclusionRGNT is a comparatively rare mixed glioneuronal tumor that occurs in the midline structures. Its morphology shows certain overlaps with other low-grade neuroepithelial tumors. Identifying the rosettes around the neuropil is critical for morphological diagnosis, and the molecular identification of FGFR1 mutations accompanied by PIK3R1 mutations can facilitate diagnosis.

Expanding the Imaging Spectrum of Polymorphous Low-Grade Neuroepithelial Tumor of the Young in Children.

Polymorphous low-grade neuroepithelial tumors of the young (PLNTY) are rare brain tumors first described in 2017 and recently included in the 2021 5th World Health Organization Classification of Tumors of the Central Nervous System. They typically affect children and young adults. Few pediatric cases have been reported in the literature. The most common imaging features described, include location within the temporal lobe, involvement of the cortical/subcortical region, coarse calcifications, and well-defined margins with solid and cystic morphology, with slight-or-no enhancement. However, there is limited information on imaging features in children. We present the imaging spectrum of neuroimaging features in a series of pediatric patients with a histologically and molecularly proved PLNTY diagnosis. Coarse calcifications are uncommon in children compared with the adult literature, and they may develop with time. The transmantle-like sign can be observed, and adjacent cortical dysplasia may be seen. Seizure recurrence may occur despite gross total resection of the tumor.

Transcriptional features of low-grade neuroepithelial tumors with the BRAF V600E mutation associated with epileptogenicity.

Low-grade neuroepithelial tumors are major causes of drug-resistant focal epilepsy. Clinically, these tumors are defined as low-grade epilepsy-associated neuroepithelial tumors (LEATs). The BRAF V600E mutation is frequently observed in LEAT and linked to poor seizure outcomes. However, its molecular role in epileptogenicity remains elusive. To understand the molecular mechanism underlying the epileptogenicity in LEAT with the BRAF V600E genetic mutation (BRAF V600E-LEAT), we conducted RNA sequencing (RNA-seq) analysis using surgical specimens of BRAF V600E-LEAT obtained and stored at a single institute. We obtained 21 BRAF V600E-LEAT specimens and 4 control specimens, including 24 from Japanese patients and 1 from a patient of Central Asian origin, along with comprehensive clinical data. We submitted the transcriptome dataset of 21 BRAF V600E-LEAT plus 4 controls, as well as detailed clinical information, to a public database. Preliminary bioinformatics analysis using this dataset identified 2134 differentially expressed genes between BRAF V600E-LEAT and control. Additionally, gene set enrichment analysis provided novel insights into the association between estrogen response-related pathways and the epileptogenicity of BRAF V600E-LEAT patients. Our datasets and findings will contribute toward the understanding of the pathology of epilepsy caused by LEAT and the identification of new therapeutic targets.

Long-term epilepsy associated-tumors (LEATs): what is new?

Long-term epilepsy-associated tumors (LEATs) include a series of neoplasms that commonly occur in children, adolescents, or young adults, have an astrocytic or glioneuronal lineage, are histologically benign (WHO grade1) with a neocortical localization predominantly situated in the temporal lobes. Clinically, chronic refractory epilepsy is usually the unique symptom. Gangliogliomas (GG) and dysembryoplastic neuroepithelial tumors (DNT) are the most common representative entities besides pilocytic astrocytomas (PA) and angiocentric gliomas (AG). Recent molecular studies have defined new clinicopathological entities, which are recognized by the WHO 2021 classification of brain tumors. Some of them such as diffuse astrocytoma MIB or MYBL1 altered, polymorphous low-grade neuroepithelial tumor of the young (PLNTY), and multilocular and vacuolating neuronal tumor (MVNT) are currently considered LEATs. The relationship between LEATs and epilepsy is still a matter of debate, and there is a general agreement about the beneficial effects of an early neurosurgical intervention on the clinical outcome.

Clinical significance of molecular subgroups of polymorphous low-grade neuroepithelial tumor of the young (PLNTY): A small single institutional case series and integrated analysis

IntroductionPolymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a recently described entity. The clinicopathological features and prognosis of the molecular subgroups of these rare tumors is poorly understood. In this study, we presented a small case series of three new cases and integrated the data with published cases in the literature to characterize the similarities and differences of molecular subgroups of PLNTY. MethodsWe searched our institutional archive for PLNTY cases and searched PubMed and Web of Science for relevant data. Demographic, clinical, radiologic, histopathological, molecular, and follow-up data of our four cases with published cases were integrated for final analyses. ResultsWe identified three institutional cases of PLNTY. The median age of our patients was 17 years (range: 13–42). All patients had a prior history of chronic seizures and all had tumors affecting the temporal lobes. Histopathologically, all cases showed oligodendroglial-like morphology with intratumoral calcifications and at least partially infiltrative growth patterns. Tumor cells were immunoreactive with CD34 and GFAP. Genetically, all cases harbored BRAF V600E mutations. Integrated analyses, including a total of 67 cases, demonstrated that PLNTYs with FGFR2 mutation were significantly younger (median age 11.0 years) than those with BRAF V600E or FGFR3 fusions (median age 41.0 and 16.0 years, respectively). All BRAF V600E-positive PLNTYs were free of tumor recurrence, while four of PLNTYs in other molecular subgroups developed tumor recurrence by imaging. ConclusionOur study suggests that PLNTYs have distinct clinicopathological features and are driven by genetic alterations in the MAPK pathway. The molecular subgroups of PLNTYs share similar findings, but also demonstrate distinct patient demographics.

Review on neuroimaging in pediatric-type diffuse low-grade gliomas.

The fifth edition of the World Health Organization Classification of Tumors of the Central Nervous System (WHO CNS5) has identified a new classification system for tumors of the brain and spinal cord, highlighting the pivotal role of molecular diagnosis in accurately categorizing neoplasms. In addition to previous classifications, one of the key distinctions lies in categorizing pediatric-type diffuse low-grade gliomas (pDLGGs) and pediatric-type diffuse high-grade gliomas (pDHGGs) as distinct tumor types. Although similar in histology and morphology, pediatric diffuse gliomas are completely different from the adult type with respect to the molecular genetic characteristics, prognosis, and treatment strategies. pDLGG includes four tumor types, namely, diffuse astrocytoma, MYB- or MYBL1-altered; angiocentric glioma; polymorphous low-grade neuroepithelial tumor of the young (PLNTY); and diffuse low-grade glioma, MAPK pathway-altered, three types of which are newly recognized tumor types. Herein, we review the clinical characteristics, histopathological and molecular genetic characteristics, neuroimaging features, and prognosis of pDLGG and summarize the neuroimaging key points in diagnosing different tumor types. This review aims to evaluate and update the relevant pDLGG features and advances in neuroimaging that may assist in differential diagnosis, surgery planning, and prognostic determination of these tumor types and provide accurate diagnostic information for clinical colleagues.

Role of endoscopic third ventriculostomy in patients undergoing resection of pulvinar area lesions: Preliminary clinical results

BackgroundPatients with pulvinar area lesions may develop hydrocephalus at any stage. The role of endoscopic third ventriculostomy (ETV) in this setting remains unclear. MethodWe retrospectively enrolled 15 patients with a mean age of 43 years who underwent endoscopic resection of pulvinar area lesions using the supracerebellar infratentorial approach (SCITA). We compared the different modalities of hydrocephalus management and their outcomes. ResultsNine of 15 patients (60.0%) had preoperative obstructive hydrocephalus. Five patients underwent ETV before tumor resection, and none developed postoperative hydrocephalus. Four patients underwent one-stage surgery for tumor removal, and one patient with a polymorphous low-grade neuroepithelial tumor of the young required postoperative ETV. Another patient with diffuse astrocytoma and hydrocephalus underwent concurrent lamina terminalis fenestration and endoscopic resection via the SCITA, which resulted in the resolution of hydrocephalus. The preoperative ETV group had no major postoperative complications, while the non-ETV group had three (0/5 vs. 3/4, P = 0.048). The ETV group also had a shorter intensive care unit stay; however, the difference was not significant (1.2 vs. 2.8; P = 0.188). ETV was effective in alleviating symptoms of postoperative hydrocephalus in patients with midbrain-invading tumors. ConclusionEndoscopic surgery via the SCITA can address both tumor and hydrocephalus issues in some cases but has a higher surgical risk and postoperative hydrocephalus rate. Preoperative ETV can prevent these complications and improve postoperative outcomes.

P20.02.B ELECTRO-CLINICAL, NEUROIMAGING FEATURES AND NEUROPATHOLOGICAL CHARACTERIZATION OF POLYMORPHOUS LOW-GRADE NEUROEPITHELIAL TUMOR OF THE YOUNG (PLNTY)

Abstract BACKGROUND Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) has been recently recognized by 2021 WHO Central nervous system classification. It is an epileptogenic tumor type, affecting mostly children and young adults, with peculiar radiological, and pathomolecular features. PLNTY is a very rare tumor, described in only 52 cases up to now. Herein, we describe 13 patients with electro-clinical and neuroimaging findings, associated to histopathological and molecular findings. MATERIAL AND METHODS We selected PLNTY patients from our Cancer Registry (Apr 2017-Dec 2022), and collected electro-clinical, radiological and histo-molecular data. Minimum follow-up was 6 months. Exams included EEG, long-term scalp video-EEG, pre-surgical brain computer tomography and Magnetic Brain Imaging (MRI). Immunohistochemistry included CD34, IDH1-R132H, GFAP, synaptophysin, ATRX, p53 and FGFR3. IDH1-2, BRAF (V600E) sequencing, Kiaa1549:BRAF, FGFR3:TACC3, FGFR2:kii1598 and FGFR2:CTNNA3 fusion analyses will be performed. RESULTS We describe 13 patients, median age 20.6 years (range 12.3-46.4). Most patients showed memory/executive impairment and had epilepsy, with an onset from 5 months-21 years before surgery. The main feature of seizures was a difficult localization and even lateralization, both semiologically and electrographically. Post-surgical seizure control was excellent.The tumors (n=11/13 temporal) presented as solid or solid-cystic cortical mass with no mass effect and unclear hedges. Calcifications were present in 4, and cysts in 6 cases. Microscopically the tumors showed infiltrative growth pattern, oligodendroglial-like cells, strong and often diffuse CD34 immunostaining, and frequent intra-tumoral calcifications. Malformation of cortical development, namely FCD type IIIB, was associated to PLNTY in 2 cases. Proliferation activity (MIB-1 LI) was very low (1%) in all cases except one (MIB-1 LI which reached 3%). CONCLUSION This study significantly extends the number of reported PLNTY associated to epilepsy, mostly characterized by bilateral interictal epileptiform discharges and difficult to lateralize seizures.The MRI features were heterogeneous and the differential diagnosis should include also dysplasia and glioneuronal tumors. PLNTY, despite its name, occurs also in adults, and electro-clinical and radiological diagnosis can be challenging. As recently described, PLNTY can show the MAPK pathway activating alterations, that are under investigation in our cohort to eventually clarify their role in the evolution of the disease. SUPPORT the study is partially supported by the Health Italian Minister (RC).

Congenital Lumbosacral Malformations with Low-Grade Neuroepithelial Tumor Causing Progressive Postpoliomyelitis Paralytic Limb.

Nothing to report.

Pemigatinib For Previously Treated Central Nervous System Tumors With Activating FGFR Mutations or Translocations: Results From FIGHT-207 (S17.004)

Pemigatinib For Previously Treated Central Nervous System Tumors With Activating FGFR Mutations or Translocations: Results From FIGHT-207 (S17.004)

Atypical presentation of polymorphous low-grade neuroepithelial tumor of young (PLNTY): a case report

The polymorphous low-grade neuroepithelial tumor of young (PLNTY) is considered as one among the low-grade neuroepithelial tumor; as per WHO-2021 classification of Brain Tumors in the fifth edition. The term PLNTY was first coined by Huse in 2016. These morphologically variable tumors are characterized by their oligodendroglioma-like cellular components, infiltrative growth pattern, and Cluster of Differentiation 34 (CD34) immunopositivity. Frequent genetic abnormalities involving mitogen-activated protein kinase pathway constituents like the BRAF proto-oncogene or fibroblast growth receptor 2/3 are harbored by PLNTYs. Radiologically, these are found to be well-circumscribed lesions with calcified and cystic components, affecting primarily temporal lobes. Clinically, they present with seizures/epilepsy in young adults (< 30 years). In the present manuscript we are reporting a case of 37-year-old male, presenting with a gradually progressive headache for 6 months, found to have a left frontal multiloculated cystic lesion with dystrophic calcifications. Based on the distinctive histopathological feature of the oligodendroglioma-like infiltrative lesion showing CD34 immunopositivity, a diagnosis of a polymorphous low-grade neuroepithelial tumor of young was made.

Pearls & Oy-sters: Salt and Pepper Sign, PLNTY for Drug-Resistant Epilepsy.

Drug-resistant epilepsy, defined as the failure of 2 or more antiseizure medications to achieve seizure freedom, is responsible for 2/3 of epilepsy cases. Tumors are responsible for up to 15% of all adult onset and up to 6% of childhood onset epilepsies. Among these tumors, commonly known subtypes DNET, ganglioglioma, and low-grade astrocytoma are often suspected. New advances in tumor classification have been made, with genetics playing a key role in tumor classification. Polymorphic low-grade neuroepithelial tumor of the young (PLNTY) is a highly epileptogenic subtype of tumors that may mimic low-grade gliomas but offer pathologic and genetic clues: oligodendroglioma-like cellular components and infiltration patterns and strong CD34-immunopositive stain. In addition, a key finding is radiologic: a unifocal abnormality best seen on MRI brain in FLAIR sequence as the "salt and pepper sign" and calcifications appreciated on CT head.

CS-10 POLYMORPHOUS LOW-GRADE NEUROEPITHELIAL TUMOR OF THE YOUNG: OUR CASE AND REVIEW OF THE LITERATURE

Abstract Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a new tumor that was officially listed in the WHO 5th edition in 2021. It is clinically and pathologically oligodendroglioma-like, but can be distinguished by CD34 positivity. Although this case was initially thought to be an oligodendroglioma-like low grade glioma, it was clinically and pathologically considered to be a typical case, so we report it here.14 year old female. No special notes, including growth and development. The patient suddenly developed a generalized tonic convulsion and was taken to the emergency room. A CT scan revealed a lesion with strong calcification in her left temporal lobe, and she was referred to our department. She had no neurological findings and underwent total resection under awake surgery. She was difficult to diagnose with intraoperative frozen section. diagnosis.The pathological findings are medium-sized oval to oblong nuclei, diffuse proliferation of tumor cells with delicate cell projections, and oligodendroglioma-like areas with perinuclear halos. A very large number of fine calcifications are observed, but necrosis and microvascular hyperplasia are not observed. GFAP, olig2, and nestin were positive, and synaptophysin, Nf, Hu C/D, MAP2, and chromograninA were negative. MIB-1 was less than 5%. The sequence was IDH1/2, TERTwild, and the BRAF-V600E mutation was recognized. Tumor cells were CD34-positive, leading to a final diagnosis of PLNTY. PLNTY is a new concept of tumor and accumulation is still small. Although this case has typical clinical and pathological features, preoperative diagnosis was difficult because it is a rare tumor. Intraoperative diagnosis is also difficult, suggesting the difficulty of diagnosing this tumor. Based on past cases, we report preoperative diagnostic imaging, intraoperative findings, and histopathological findings, including literature considerations.

Varied histomorphology and clinical outcomes of FGFR3-TACC3 fusion gliomas.

Targeted therapies for driver gene fusions in cancers have yielded substantial improvements in care. Here, the authors outline a case series of 6 patients with FGFR3-TACC3 fusion in primary brain tumors ranging from polymorphous low-grade neuroepithelial tumor of the young to papillary glioneuronal tumors and glioblastoma (GBM). Previous studies indicated the FGFR3-TACC3 fusion provides survival benefit to GBM patients. Consistent with this, 2 patients with GBM had unexpectedly good outcomes and survived for 5 and 7 years, respectively. In contrast, 2 patients with initially lower graded tumors survived only 3 years and 1 year, respectively. One patient received erdafitinib, a targeted FGFR inhibitor, for 3 months at late disease recurrence and no response was seen. There were varied histomorphological features, including many cases that lacked the characteristic FGFR3-TACC3 pathology. The findings of this cohort suggest that molecular testing is justified, even for glioma cases lacking classic histopathological signatures. Currently, FGFR3-TACC3 fusion gliomas are often classified on the basis of histopathological features. However, further research is needed to examine whether IDH1/2-wild-type tumors with FGFR3-TACC3 fusion should be classified as a subtype on the basis of this molecular fusion. Because patients with IDH1/2-wild-type GBM with FGFR3-TACC3 fusion have improved survival, routine molecular testing for this mutation in patients enrolled in clinical trials and subsequent stratification may be warranted.

NIMG-95. IMAGING CHARACTERISTICS OF POLYMORPHOUS LOW GRADE NEUROEPITHELIAL TUMOR (PLNTY)

Abstract Polymorphous low grade neuroepithelial tumor of the young (PLNTY) was first described in 2017 in the pathology literature based on the unique histologic and molecular characteristics. Most of the patients in the original article presented with seizures linked to a temporal lobe lesion. We report a pediatric patient who presented with seizures found to have a lesion which was consistent with PLNTY on biopsy. We will review the radiology and pathology of this case with a quick review of the characteristic findings of PLNTY.

Endoscopic resection of thalamic lesions via supracerebellar infratentorial approach: a case series and technical note.

The deep location of the thalamus and the complex neural circuits in the surrounding area make surgery extremely challenging. Feasibility and advisability of using a supracerebellar infratentorial approach (SCITA) for endoscopic resection of thalamic lesions remains to be further evaluated. Fifteen patients who underwent endoscopic resection of thalamic via SCITA from 2014 to 2021 were retrospectively collected. We analyzed preoperative tumor-related variables and surgical procedures in detail, as well as postoperative outcomes. Lesions mainly located in the posterior and/or medial part of the thalamus, and some of them expanded downward, or backward. The mean size of them was 30 × 24mm. Five of the nine patients with preoperative hydrocephalus underwent cerebrospinal fluid shunts to relieve increased intracranial pressure. Among the 15 patients, 4 were glioblastoma, 3 were pilocytic astrocytoma, and the rest included 1 case of anaplastic astrocytoma, melanoma, polymorphous low-grade neuroepithelial tumor of the young, rosette-forming glioneuronal tumor, inflammatory lesion, diffuse midline glioma, and cavernous hemangioma. The majority of patients (10/15) achieved gross total resection, which has become more pronounced since paramedian SCITA was used in place of the midline approach in 2020 (6/8). Three patients had unresolved or new onset of clinical symptoms after surgery, resulting in a decreased KPS score at discharge. Neuro-endoscopic techniques can ameliorate many of the shortcomings of the SCITA. With the accumulation of experience and technological progress, more deficiencies of this approach may be improved, enabling safe and effective resection of posterior and/or medial part thalamic lesions.