Imaging of pediatric glioneuronal and neuronal tumors.

Glioneuronal tumors (GNTs) are an expanding group of primary CNS neoplasms, commonly affecting children, adolescents and young adults. Most GNTs are relatively indolent, low-grade, WHO grade I lesions. In the pediatric age group, GNTs have their epicenter in the cerebral cortex and present with seizures. Alterations in the mitogen-activated protein kinase (MAPK) pathway, which regulates cell growth, are implicated in tumorigenesis. Imaging not only plays a key role in the characterization and pre-surgical evaluation of GNTs but is also crucial role in follow-up, especially with the increasing use of targeted inhibitors and immunotherapies. In this chapter, we review the clinical and imaging perspectives of common pediatric GNTs.

Long-term seizure outcome after epilepsy surgery of neuroglial tumors.

Purpose: Neuroglial tumors are frequently associated with pharmacorefractory epilepsies. However, comprehensive knowledge about long-term outcomes after epilepsy surgery and the main prognostic factors for outcome is still limited. We sought to evaluate long-term outcomes and potential influencing factors in a large cohort of patients who underwent surgery for neuroglial tumors in a single-center setting. Methods: The study analyzed the outcomes of 107 patients who underwent epilepsy surgery for neuroglial tumors between 2001 and 2020 at the Department of Epileptology, University Hospital Bonn, in Germany. The outcomes were evaluated using Engel classification. Differences in outcome related to potential prognostic factors were examined using the Chi2-test, Fisher's exact test and sign test. Additionally, stepwise logistic regression analysis was employed to identify independent prognostic factors. Results: Complete seizure freedom (Engel Class IA) was achieved in 75% of the operated patients at 12 months, and 56% at the last follow-up visit (70.4 ± 6.2 months, median: 40 months). Completeness of resection was a crucial factor for both 12-month follow-up outcomes and the longest available outcomes, whereas lobar tumor localization, histology (ganglioglioma vs. dysembryoplastic neuroepithelial tumor), history of bilateral tonic-clonic seizures prior to surgery, invasive diagnostics, side of surgery (dominant vs. non-dominant hemisphere), age at epilepsy onset, age at surgery, and epilepsy duration did not consistently impact postsurgical outcomes. Among temporal lobe surgeries, patients who underwent lesionectomy and lesionectomy, including hippocampal resection, demonstrated similar outcomes. Conclusion: Neuroglial tumors present as excellent surgical substrates in treating structural epilepsy. To achieve an optimal postsurgical outcome, a complete lesion resection should be pursued whenever possible.

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

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Emerging insights into cephalic neural crest disorders: A single center experience.

Objectives: Neural crest cells (NCCs) are transient structures in the fetal life in vertebrates, which develop at the junctional site of the non-neural and neural ectoderm, sharing a common developmental origin for diverse diseases. After Epithelio-mesenchymal (EMT) of the NCCs within the neural tube, delamination of NCCs occurs. After delamination, the transformation of these cells into various cell lineages produces melanocytes, bones, and cartilage of the skull, cells of the enteric and peripheral nervous system. After the conversion, these cells migrate into various locations of the entire body according to the cell lineage. Abnormalities in neural crest (NC) formation and migration result in various malformations and tumors, known as neurocristopathy. Material and Methods: Herein, this case series describes a single-center experience in cephalic NC disorders over the past 3 years, including 17 cases of varying composition (i.e., vascular, dysgenetic, mixed, and neoplastic forms) involving the brain and occasionally skin, eyes, and face of the patients. Results: In our study of 17 patients with cephalic NC disease, 6 (35.3%) patients had vascular form, 5 (29.4%) had dysgenetic form, 4 (23.5%) had mixed form, and 2 (11.7%) had neoplastic form. Brain involvement in the form of vascular or parenchyma or both vascular and parenchymal was seen in all of our patients (100%), skin in 6 (35.3%) patients, eye in 2 (11.7%), and face in 1 (5.9%) patient. Treatment was planned according to the various manifestations of the disease. Conclusion: Neural crest diseases (NCDs) are a rare and under-recognized group of disorders in the literature and may have been under-reported due to a lack of awareness regarding the same. More such reporting may increase the repertoire of these rare disorders such that clinicians can have a high degree of suspicion leading to early detection and timely counseling and also improve preventive strategies and help in developing new drugs for these disorders or prevent them.

Bright diffusion sign: A sensitive and specific radiologic biomarker for multinodular and vacuolating neuronal tumor.

BACKGROUND AND PURPOSE: Accurate differentiation between multinodular and vacuolating neuronal tumor (MVNT) and dysembryoplastic neuroepithelial tumor (DNET) is important for treatment decision-making. We aimed to develop an accurate radiologic diagnostic model for differentiating MVNT from DNET using T2WI and diffusion-weighted imaging (DWI). MATERIALS AND METHODS: A total of 56 patients (mean age, 47.48±17.78 years; 31 women) diagnosed with MVNT (n = 37) or DNET (n = 19) who underwent brain MRI, including T2WI and DWI, were included. Two board-certified neuroradiologists performed qualitative (bubble appearance, cortical involvement, bright diffusion sign, and bright apparent diffusion coefficient [ADC] sign) and quantitative (nDWI and nADC) assessments. A diagnostic tree model was developed with significant and reliable imaging findings using an exhaustive chi-squared Automatic Interaction Detector (CHAID) algorithm. RESULTS: In visual assessment, the imaging features that showed high diagnostic accuracy and interobserver reliability were the bright diffusion sign and absence of cortical involvement (bright diffusion sign: accuracy, 94.64 %; sensitivity, 91.89 %; specificity, 100.00 %; interobserver agreement, 1.00; absence of cortical involvement: accuracy, 92.86 %; sensitivity, 89.19 %; specificity, 100.00 %; interobserver agreement, 1.00). In quantitative analysis, nDWI was significantly higher in MVNT than in DENT (1.52 ± 0.34 vs. 0.91 ± 0.27, p < 0.001), but the interobserver agreement was fair (intraclass correlation coefficient = 0.321). The overall diagnostic accuracy of the tree model with visual assessment parameters was 98.21 % (55/56). CONCLUSION: The bright diffusion sign and absence of cortical involvement are accurate and reliable imaging findings for differentiating MVNT from DNET. By using simple, intuitive, and reliable imaging findings, such as the bright diffusion sign, MVNT can be accurately differentiated from DNET.

Posterior Fossa Dysembryoplastic Neuroepithelial Tumor: A Neuropathological Report.

Dysembryoplastic neuroepithelial tumors (DNTs) are rare neoplastic entries of the central nervous system. Conventionally DNTs are with cortical location and predominantly occur in the temporal lobe associated with epilepsy. Subtentorial DNTs are rare entries. Herein we report a case of a two-year-old female with a DNT located in the cerebellum. The patient presented clinically with new onset gait instability, headaches and strabismus. Neuroradiology revealed a heterogenous, predominantly cystic lesion in the cerebellar vermis and left cerebellar hemisphere, which was interpreted as possible medulloblastoma based on the patient profile. Frozen section neuropathology was more suggestive of a low-grade glial tumor, with conventional histology and immunohistochemistry showing an admixture of glial and neuronal cells - a complex variety of DNT. Due to the histological appearance, differential diagnosis was required with other neuroglial tumors native to the posterior fossa, such as Lhermitte-Duclos disease. There have been several such published case reports, which, although of older patients, present with similar symptoms and neuropathological findings. The complexity of the neuropathological finding in posterior fossa DNTs can lead to future separation of this entry from conventional DNT, as was seen in the past with septum pellucidum DNT, now referred to as myxoid glioneuronal tumor.

Association between features of intraoperative ultrasound and magnetic resonance imaging in the diagnosis of dysembryoplastic neuroepithelial tumor.

Background: To analyze the characteristics of images from intraoperative ultrasound (IoUS) and preoperative magnetic resonance imaging (MRI) and their relationship with pathological components of dysembryoplastic neuroepithelial tumor (DNT) and to discuss the role of IoUS in detecting tumor residues. Methods: The clinical and image data of 24 patients with postoperative pathology-confirmed DNT were analyzed retrospectively. Baseline characteristics, imaging features, and intraoperative residues were recorded for further analysis. Cohen's kappa consistency evaluation was performed on the echo and signal characteristics of the lesions. Results: Cohen's kappa coefficient between the echo and signal of the lesion was 0.832. The characteristics of IoUS were gyrus or mass hyperechoic solid nodules located under the cortex, insufficient blood flow signals, and clear boundaries, in addition to mixed cystic and solid echo nodules. The solid part of the lesion consisted of pathologically nodular specific glioneuronal element (SGE) or was combined with glial nodules and focal cortical dysplasia (FCD), which was characterized by a high echo or long T1 long T2 signal and uniform or uneven distribution. The cystic part consisted of a mucinous matrix, showing echoless or long T1 long T2 on fluid attenuated inversion recovery (FLAIR), which was higher than that in cerebrospinal fluid but lower than that in the cerebral cortex. The residual lesion discovered using IoUS was confirmed with postoperative MRI. Conclusions: The IoUS characteristics of DNT are strongly consistent with MRI, and its imaging features are related to pathological components. IoUS can assist the operator to judge the mode and scope of tumor resection, detect residual tumor, and improve the rate of total tumor resection.

Central nervous system involvement in individuals with RASopathies.

Central nervous system (CNS) anomalies are common in individuals with RASopathies. While certain findings, including relative or absolute macrocephaly, are typical for most RASopathies, other findings are more common in certain conditions, with rare low-grade gliomas in Noonan syndrome (NS); Chiari 1 malformation and tethered cord in Costello syndrome (CS); and variable structural anomalies including heterotopia and hydrocephalus in cardio-facio-cutaneous syndrome (CFC). We performed a literature review and present aggregate data on the common and uncommon CNS manifestations in individuals with RASopathies. A gene-based approach to defining risk for specific abnormalities may be considered. However, limited information on the CNS findings of rare RASopathies, such as autosomal recessive LZTR1-related NS or PPP1CB-related NS with loose anagen hair (NSLH), is currently available. Thus, consideration of the RASopathies as a group of distinct syndromic conditions with shared underlying causes and overlapping clinical presentations remains relevant, and individuals with a RASopathy are at risk for many findings seen in these conditions.

Early Epilepsy Surgery in Benign Cerebral Tumors: Avoid Your 'Low-Grade' Becoming a 'Long-Term' Epilepsy-Associated Tumor.

Epilepsy surgery in low-grade epilepsy-associated neuroepithelial tumors (LEAT) is usually evaluated in drug-resistant cases, often meaning a time delay from diagnosis to surgery. To identify factors predicting good postoperative seizure control and neuropsychological outcome, the cohort of LEAT patients treated with resective epilepsy surgery at the Epilepsy Center Frankfurt Rhine-Main, Germany between 2015 and 2020 was analyzed. Thirty-five patients (19 males (54.3%) and 16 females, aged 4 to 40 years (M = 18.1), mean follow-up 33 months) were included. Following surgery, 77.1% of patients remained seizure-free (Engel IA/ILAE 1). Hippocampus and amygdala resection was predictive for seizure freedom in temporal lobe epilepsy. In total, 65.7% of all patients showed cognitive deficits during presurgical workup, decreasing to 51.4% after surgery, predominantly due to significantly less impaired memory functions (p = 0.011). Patients with presurgical cognitive deficits showed a tendency toward a longer duration of epilepsy (p = 0.050). Focal to bilateral tonic-clonic seizures (p = 0.019) and young age at onset (p = 0.018) were associated with a higher likelihood of cognitive deficits after surgery. Therefore, we advocate early epilepsy surgery without requiring proof of drug-resistance. This refers especially to lesions associated with the non-eloquent cortex.

A Constellation of Atypical Findings in a Nine-Year-Old Child With Dysembryoplastic Neuroepithelial Tumors: A Case Report and Review of the Literature.

Dysembryoplastic neuroepithelial tumors (DNETs) are rare, generally benign, mixed neuronal-glial neoplasms occurring most often between 10 and 14 years of age. These lesions are classically cortically based and solitary, found preferentially in the temporal lobe, and most commonly present with seizures. On magnetic resonance imaging (MRI), these lesions are generally cystic and have variable contrast enhancement, which, when present, often involves the periphery. Rarely, lesions followed radiographically may demonstrate delayed contrast enhancement. Here, we present a case of multifocal DNETs involving the cerebellum that demonstrated delayed contrast enhancement. In addition, these occurred in a patient with Noonan syndrome (NS), a "RASopathy" disorder associated with low-grade glial and glioneuronal tumors. We present a summary of all previously reported cases of cerebellar DNETs. Our patient was successfully treated surgically and is doing well clinically, now one year status post his last procedure, and is being closely monitored with serial MRIs for progression. Gross total resection is often curative without adjuvant therapy for most DNETs. Our case emphasizes the importance of radiographic surveillance, as multifocality and recurrence may necessitate more than one procedure. Lastly, clinicians should be suspicious for DNETs and other low-grade glial tumors when treating patients with NS, acknowledging their predisposition for multifocal involvement and atypical presentations.

Dysembryoplastic Neuroepithelial Tumor of the Infratentorial Multiple Lesions: A Case Report and Review of the Literature.

A dysembryoplastic neuroepithelial tumor (DNT) is a benign neoplasm that usually occurs in the supratentorial cerebral cortex. Here, we report a rare case of an infratentorial DNT in a 42-year-old woman who presented with dizziness and a gait disturbance. Magnetic resonance imaging of the lesion demonstrated hyperintensity on T2-weighted images and hypointensity on T1-weighted images of the left cerebellar hemisphere with a multifocal lesion. Macroscopically, the lesion appeared soft, avascular, and slightly torose at the cortical surface. Histologically, dysplastic disorganization of the cortex and floating neurons were observed. The pathological and immunochemical features of this case agree with the diagnosis of a DNT. The lesion partially included cortical heterotopia, which is a novel observation in an infratentorial DNT. On the basis of the previous reports, we discussed the surgical resection of the infratentorial DNT.

From a dysembryoplastic neuroepithelial tumor to a glioblastoma multiforme: Pitfalls of initial diagnosis on biopsy material, a case report.

BACKGROUND: Ganglioglioma (GG) and dysembryoplastic neuroepithelial tumor (DNET) belong to the group of low-grade epilepsy-associated tumors (LEAT) and are the most prevalent tumor types found in patients undergoing epilepsy surgery. Histopathological differentiation between GG and DNET can be difficult on biopsies due to limited tumor tissue. CASE DESCRIPTION: Here, we present a rare case where a low-grade tumor was initially classified as DNET, based on biopsy findings and unfortunately dedifferentiated within 10 years into a glioblastoma multiforme. After gross total resection, the initial tumor was reclassified as GG. CONCLUSION: This case illustrates the diagnostic challenges of LEAT, especially on biopsy material. Therefore, we advocate to counsel for complete resection and histopathological diagnosis utilizing tumor markers to confirm the nature of the tumor and to advice type of follow-up and eventual concurrent treatment.

Malignant transformation of a dysembryoplastic neuroepithelial tumor presenting with intraventricular hemorrhage.

Dysembryoplastic neuroepithelial tumors (DNTs) are benign brain tumors classified as grade 1 in the 2021 World Health Organization (WHO) classification of central nervous system tumors. DNTs rarely undergo malignant transformation and cause symptomatic intracranial hemorrhage. We report a case of malignant transformation of DNT presenting with intraventricular hemorrhage and review the literature on malignant transformation of DNTs. An 18-year-old woman with a history of epilepsy presented with a sudden headache and vomiting. Radiological examination revealed a mass lesion in the left parietal lobe and intraventricular hemorrhage. The patient underwent an emergency craniotomy for brain tumor resection. The lesion was pathologically diagnosed as a malignant transformation of DNT. She had been followed up without tumor recurrence for 2 years after surgery.

Challenges in the Intraoperative Consultation of Low-Grade Epilepsy-Associated Neuroepithelial Tumors by Cytomorphology in Squash Preparations.

INTRODUCTION: Low-grade epilepsy-associated neuroepithelial tumors (LEATs) create a diagnostic challenge in daily practice and intraoperative pathological consultation (IC) in particular. Squash smears are extremely useful in IC for accurate diagnosis; however, the knowledge on cytopathologic features of LEATs is based on individual case reports. Here, we discuss the 3 most common and well-established entities of LEATs: ganglioglioma (GG), dysembryoplastic neuroepithelial tumor (DNT), and papillary glioneuronal tumor (PGNT). METHODS: Thirty patients who underwent surgery for GG, DNT, and PGNT between 2001 and 2021 were collected. Squash smears prepared during intraoperative consultation were reviewed by 1 cytopathologist and an experienced neuropathologist. RESULTS: Among the 30 tumors, 16 (53.3%) were GG, 11 (36.6%) DNT, and 3 (10%) PGNT. Cytomorphologically, all of the 3 tumor types share 2 common features such as dual cell population and vasculocentric pattern. GG smears were characteristically composed of dysplastic ganglion cells and piloid-like astrocytes on a complex architectural background of thin- to thick-walled vessels. DNT, on the other hand, showed oligodendroglial-like cells in a myxoid thin fibrillary background associated with a delicate capillary network. Common cytological features of PGNT were hyperchromatic cells with narrow cytoplasm surrounding hyalinized vessels forming a pseudopapillary pattern and bland cells with neuroendocrine nuclei dispersed in a neuropil background. CONCLUSION: A higher diagnostic accuracy can be obtained when squash smears are applied with frozen sections. However, it is important to integrate clinical and radiologic features of the patient as well as to know the cytopathologic features of the LEAT spectrum in the context of differential diagnosis to prevent misinterpretation in the IC.

Integrated genotype-phenotype analysis of long-term epilepsy-associated ganglioglioma.

The BRAF p.V600E mutation is the most common genetic alteration in ganglioglioma (GG). Herein, we collected a consecutive series of 30 GG specimens from Xuanwu Hospital in order to corroborate the genetic landscape and genotype-phenotype correlation of this enigmatic and often difficult-to-classify epilepsy-associated brain tumor entity. All specimens with histopathologically confirmed lesions were submitted to targeted next-generation sequencing using a panel of 131 genes. Genetic alterations in three cases with histologically distinct tumor components, that is, GG plus pleomorphic xanthoastrocytoma (PXA), dysembryoplastic neuroepithelial tumor (DNT), or an oligodendroglioma (ODG)-like tumor component, were separately studied. A mean post-surgical follow-up time-period of 23 months was available in 24 patients. Seventy seven percent of GG in our series can be explained by genetic alterations, with BRAF p.V600E mutations being most prevalent (n = 20). Three additional cases showed KRAS p.Q22R and KRAS p.G13R, IRS2 copy number gain (CNG) and a KIAA1549-BRAF fusion. When genetically studying different histopathology patterns from the same tumor we identified composite features with BRAF p.V600E plus CDKN2A/B homozygous deletion in a GG with PXA features, IRS2 CNG in a GG with DNT features, and a BRAF p.V600E plus CNG of chromosome 7 in a GG with ODG-like features. Follow-up revealed no malignant tumor progression but nine patients had seizure recurrence. Eight of these nine GG were immunoreactive for CD34, six patients were male, five were BRAF wildtype, and atypical histopathology features were encountered in four patients, that is, ki-67 proliferation index above 5% or with PXA component. Our results strongly point to activation of the MAP kinase pathway in the vast majority of GG and their molecular-genetic differentiation from the cohort of low-grade pediatric type diffuse glioma remains, however, to be further clarified. In addition, histopathologically distinct tumor components accumulated different genetic alterations suggesting collision or composite glio-neuronal GG variants.

Association of CT and MRI Manifestations with Pathology in Dysembryoplastic Neuroepithelial Tumors.

Objective: To investigate the CT, MRI and pathological features of dysembryoplastic neuroepithelial tumor (DNET). Methods: The CT and MRI features of six cases of pathologically confirmed DNET were retrospectively analyzed and compared with pathology. Results: All six cases of DNET were solitary, and lesion in one case was located in the right parietal lobe, one case in the right frontal lobe, one case in the cerebellar vermis, one case in the right temporo-parietal occipital lobe, one case in the left basal ganglia, and one case in the pineal gland. CT and MRI showed cystic solid tumor in all six cases, of which four showed calcification. In CT images, the cystic components appeared low-density, solid nodules, septa, and cyst walls were slightly high-density, and calcifications were high-density. In MRI images, the cystic components were hypointense on T1WI and hyperintense on T2WI, solid nodules, septa and cyst walls were iso-intense or slightly hyperintense on T1WI and T2WI sequences, and calcifications were all hypointense. On enhanced scan, the cystic components were not enhanced, and the solid nodules, septa, and cyst walls were inhomogeneously enhanced. Conclusion: The imaging manifestations of DNET are characteristic, and the combination of clinical and imaging features can greatly improve diagnostic accuracy.

Clinical and histopathological profile of dysembryoplastic neuroepithelial tumor: An experience from a tertiary care center.

INTRODUCTION: Dysembryoplastic neuroepithelial tumor (DNT) is a rare benign brain tumor predominantly involving children and young adults. Histologically, it corresponds to WHO Grade I tumors; however, it may masquerade aggressive neural tumors such as oligodendroglioma, oligoastrocytoma, pilocytic astrocytoma, and ganglioglioma. The literature on clinical, radiological, and pathological spectrum of DNT is described mostly in the form of case reports, with only a few case series reported till date. METHODS: A retrospective review of files with diagnosis of DNT (2016 to 2018) was made in the Department of Pathology, National Institute of Pathology, New Delhi. A total of ten cases were retrieved, and their clinical, radiological, and histopathological features were reviewed and studied. Special stains and immunohistochemistry were done, wherever required. RESULTS: The mean age was 14.8 (±7.9) years, with a male-to-female ratio of 1.5:1. The most common mode of presentation was recurrent, intractable seizures. The most common site of lesion was parietal lobe followed by temporal and frontal lobes of the brain. On histology, mucoid matrix admixed with floating neurons and oligodendrocyte-like cells was a consistent feature; however, the presence of specific glioneuronal elements was observed in only a few cases. CONCLUSIONS: DNT is a benign, low-grade, nonrecurrent neuroepithelial neoplasm. It is important to differentiate this rare entity from other mimickers, as it is surgically curable and carries an excellent prognosis without the need for adjuvant chemotherapy and radiotherapy. The study helps to enrich the clinicopathological aspects of this rare but important entity.

Intraventricular dysembryoplastic neuroepithelial tumor in the temporal horn with Broad involvement of the ependyma.

Though typical dysembryoplastic neuroepithelial tumors (DNETs) are located in the cerebral cortex, an atypical DNET could occur in the temporal horn of the lateral ventricle and broadly involve the ependyma. Awareness of this atypical form of DNET is of value for the wright diagnosis and management of atypical DNETs.

A case of a rosette-forming glioneuronal tumor with clinicopathological features of a dysembryoplastic neuroepithelial tumor and fibroblast growth factor receptor 1 internal tandem duplication.

Rosette-forming glioneuronal tumors (RGNTs) are benign WHO grade 1 tumors that occur in the ventricular system, particularly the fourth ventricle. RGNTs and dysembryoplastic neuroepithelial tumors (DNTs) are both categorized as neuronal and mixed neuronal-glial tumors and may be difficult to distinguish. Coexistence of the two tumor types has been reported. Here, we report a pediatric case of RGNT with DNT-like features showing intraventricular dissemination. The tumor occurred in the medial temporal lobe and presented with specific pathological glioneuronal elements including floating neurons, which are typical in DNTs, but was diagnosed as RGNT because of the presence of neurocytic rosettes. Genetic analysis detected fibroblast growth factor receptor 1 internal tandem duplication (FGFR1-ITD) of the tyrosine kinase domain, which was previously reported to be specific for DNT. RGNTs with FGFR1-ITD may show atypical clinical presentation and pathological features.