Pilocytic Research Articles

NFS-17. CORRELATIONS BETWEEN OPTICAL COHERENCE TOMOGRAPHY AND MAGNETIC RESONANCE IMAGING IN NEUROFIBROMATOSIS TYPE 1 – RELATED OPTIC PATHWAY GLIOMAS

Abstract BACKGROUND Optic pathway glioma (OPG) is a prevalent tumor affecting children with Neurofibromatosis type 1 (NF1), representing a diagnostic hallmark. OPGs, typically WHO grade 1 pilocytic astrocytomas, are characterized by an indolent course. Diagnosis and surveillance traditionally rely on Magnetic Resonance Imaging (MRI). Routine NF1 pediatric surveillance includes annual eye examinations, encompassing visual acuity (VA) and Optical Coherence Tomography (OCT), with MRI reserved for ophthalmological abnormalities. However, the precise correlation between altered OCT findings and OPG presence or size remains unclear, while the role of MRI in screening is contentious due to cost and anesthesia requirements. METHODS In this retrospective study, we sought to establish correlations between OCT changes and MRI-observed tumor volume in NF1-diagnosed children at a tertiary center. Clinical and ophthalmological data, including VA, fundoscopy, and OCT, were collected. Tumor volumes were assessed using the software Sophia DDMTM for Radiomics in two consecutive MRI scans in a randomly selected cohort of 50 untreated patients. RESULTS Among 409 NF1 patients, 132 (31%) were diagnosed with OPG (48% females = 64), revealing a significant association with plexiform neurofibroma (pNF) (p=0.03), thus indicating an elevated risk of concurrent tumor development. In the subcohort of patients in whom volumetric analysis was performed, the mean age at OPG diagnosis was 5.56 ± 3.59 years. While tumor volume on MRI correlated with VA (p=0.0007), OCT values did not: larger OPGs did not consistently result in thinner retinal nerve fiber layers, suggesting independence between OCT alterations and OPG size. CONCLUSIONS The observed lack of correlation among VA, retinal thickness (OCT), and tumor volume (MRI) underscores the importance of MRI as the gold standard for diagnosis. The strong association between pNFs and OPGs suggests considering whole-body MRI when an OPG is detected, facilitating comprehensive evaluation in NF1 patients.

LGG-24. PEDIATRIC GANGLIOGLIOMA WITH GERMLINE BRCA2 MUTATION

Abstract BACKGROUND BRCA1 and BRCA2 are genes associated with breast and ovarian cancer development in adults. Their influence on brain tumor formation is less understood. METHODS Retrospective review RESULTS An 11 year-old girl was diagnosed with ganglioglioma after presenting with seizures. Tumor sequencing revealed three mutations: a PDAP1-BRAF fusion, a BRAF-HIP1 non-canonical fusion, and a pathogenic BRCA2 variant D252*fs. Upon further review, a family history of breast cancer in the grandmother and several great-aunts was identified, and genetic testing confirmed this mutation to be germline. We then conducted an institutional review and identified a second pediatric low-grade glioma (pilocytic astrocytoma) patient with a pathogenic mutation in BRCA2 (T3085Fs*26) in addition to a BRAF-KIAA1549 fusion; the family declined germline BRCA2 testing. BRCA1/2 knockout models have demonstrated that both genes play a role in brain development. Concurrent BRCA2 and TP53 loss triggers formation of early onset murine medulloblastoma, a finding not observed with TP53 loss alone. In human patients, heterozygous and biallelic mutations in BRCA2 were identified as risk factors for medulloblastoma development in a recent integrative genomic analysis. Retrospective review CONCLUSION We report two cases of BRCA2 mutation in pediatric low-grade gliomas, one of which was confirmed to be germline. While somatic variants of BRCA2 have been reported in both high- and low-grade glioma, their role in these tumors has not been established to date. The BRCA2 tumor predisposition syndrome increases the risk of some types of brain tumors such as medulloblastoma, although the risk remains low compared to the risk of developing breast or ovarian cancer later in life. More evidence is required to determine whether BRCA2 germline mutations can similarly increase the risk of glioma formation.

MDB-30. ZOLPIDEM, A PROMISING DRUG TO IMPROVE POSTOPERATIVE CEREBELLAR MUTISM SYNDROME (CMS): RETROSPECTIVE STUDY OF 19 PEDIATRIC PATIENTS WITH POSTERIOR FOSSA TUMORS

Abstract INTRODUCTION Postoperative Cerebellar Mutism Syndrome (CMS) affects up to 25% of patients undergoing surgeries for posterior fossa (PF) tumors. There is no established treatment for CMS, although zolpidem has become widespread after reporting remarkable responses in some cases. However, there is very limited scientific evidence, prompting us to document our experience with zolpidem. OBJECTIVES To evaluate the efficacy and safety of zolpidem in patients with postoperative CMS in PF tumors. METHODS Observational, descriptive, retrospective study conducted at our institution. Patients <21 years diagnosed with CMS following PF tumor surgery between 2011-2023 and treated with zolpidem were included. Demographic and clinical data, therapies, CMS scales, and outcomes were collected. RESULTS Nineteen patients met the criteria, 84% males, median age 8 years (range, 9 months-19 years), and median follow-up time 30 months (range, 2-126). Diagnoses included 58% medulloblastoma, 21% pilocytic astrocytoma, 10.5% ependymoma, 10.5% others. CMS mutism scale was rated mild, moderate and severe in 5%, 21% and 74%, respectively. Median zolpidem administration was 31 days (range, 2-241) and median maximum dose was 0.25 mg/kg/day (range, 0.10-0.90). Mutism scores improved in 37% (7/19), 53% (8/15) and 64% (9/14) of patients that received zolpidem for at least 48h, 7 and 14 days, respectively. Subjective improvement in communication and interaction was observed in 74% (14/19). Only three patients with mild somnolence and one with initial irritability and insomnia were reported. CONCLUSIONS To our knowledge, this is the largest study of patients treated with zolpidem for CMS. A considerable proportion of children improved their language abilities within the first 24-48h, but some patients may even benefit from more prolonged treatment. Most children showed an adequate tolerance with very few side effects. Further studies are urgently needed, preferably within a randomized clinical trial, to find the real efficacy, appropriate dosage, and duration of zolpidem.

MODL-08. PATIENT-DERIVED ORGANOIDS RECAPITULATE THE MOLECULAR LANDSCAPE OF PEDIATRIC BRAIN TUMORS

Abstract BACKGROUND Pediatric brain tumors (PBT) are the leading cause of non-accidental death in pediatric age. These tumors are rare and lack adequate experimental models capable of accurately capturing their complex molecular landscape. METHODS AND RESULTS Our team has established specific protocols for the generation and expansion of ex-vivo patient-derived organoids (PDO) from fresh surgical material of a variety of PBT, within a clinically relevant timeframe. These include pilocytic astrocytomas, a pleomorphic xanthoastrocytoma, a rosette-forming glioneuronal tumor, a supratentorial ependymoma, diffuse high-grade gliomas, a medulloblastoma, an atypical teratoid rhabdoid tumor, and a meningioma. The PDO cultures were set within 7-15 days, with organoids reaching 200-800 μm in diameter. Immunofluorescence analysis using confocal high-content microscopy imaging revealed that PDO kept the protein markers typically found in the corresponding primary tumors. Likewise, at a genomic level, PDO recapitulated the molecular landscape of corresponding primary tumors, as denoted by the maintenance of NF1, PIK3CA, and FGFR1mutations (rosette-forming glioneuronal tumor), KIAA1549::BRAF fusions (pilocytic astrocytomas), ZFTA::RELA fusion(supratentorial ependymoma) or gene amplifications, such as KRAS, CDK4, MDM2, GLI1, PTPN11 and PI3KCA. Additionally, PDO exhibited minimal genetic drift after over one month in culture. In three PBT cases from a medulloblastoma, an atypical teratoid rhabdoid tumor, and a meningioma, where no molecular alterations were detected using a comprehensive NGS panel, we are running DNA methylation arrays and copy number variations. CONCLUSIONS Our results underscore the potential of PDO as a robust ex-vivo experimental model. The generated PDO cultures can be rapidly established and retain key molecular features of corresponding primary tumors. This preclinical model presents versatile applications, serving as a valuable molecular tool for precision medicine approaches in PBT patients, the study of PBT biology, and the acceleration of drug development processes within the context of PBT.

LGG-35. ROBUST TUMOR RESPONSE TO CHEMOTHERAPY IN THALAMIC PILOCYTIC ASTROCYTOMA WITH LARGE CYSTIC COMPONENT: A CASE REPORT

Abstract BACKGROUND Pilocytic astrocytoma (PA) is the most common glioma in children. Prognosis is excellent when complete resection is achievable. However, in central locations, such as optic pathway, thalamus, and brainstem, resection may lead to extensive morbidity, necessitating alternative treatment strategies. Chemo- and targeted therapy options have demonstrated efficacy in controlling tumor growth and providing clinical benefit; however, cystic portions are not typically responsive to either option. METHODS Case report, Retrospective chart review RESULTS A 4-year-old male presented with left sided weakness and ventriculomegaly. MRI of the brain revealed a 3.5 x 3.3 x 4.4 cm mixed solid and cystic enhancing mass extending from the right thalamus down to the right middle cerebellar peduncle. An endoscopic third ventriculostomy and tumor biopsy was performed. Histology confirmed PA, WHO Grade 1. Sequencing confirmed BRAF-KIAA1549 fusion. Chemotherapy was initiated with Carboplatin and Vincristine. Each subsequent MRI of the brain obtained during therapy and at the end of therapy demonstrated significant decrease in both solid and cystic portion of the tumor with complete resolution of symptoms and neurologic deficits. End of therapy MRI demonstrated 1.2 x 1.4 x 1.2 cm mixed solid and cystic mass. CONCLUSIONS The unique aspect of this case is the exceptional and robust response achieved in both solid and cystic components, challenging the historical notion of cystic lesions being less sensitive to chemotherapy. This observation can contribute valuable insights to the evolving understanding of treatment responses in these tumors.

NFS-19. ATYPICAL PRESENTATION OF GLIOMAS IN ADOLESCENTS WITH NEUROFIBROMATOSIS TYPE 1 (NF1): A CASE SERIES

Abstract BACKGROUND Patients with NF1 are at risk for developing gliomas, usually low-grade in childhood but may be high-grade in adults. In children, the most common sites of disease are the optic pathway and brainstem; tumors in these regions often arise in young children and display histological features characteristic of pilocytic astrocytoma (PA) when biopsied. Typical MRI findings include T2 hyperintense, T1 hypointense lesions with minimal contrast enhancement and no diffusion restriction. Due to the well-established pattern of low-grade tumor formation in children with NF1, as well as the surgically challenging areas in which these tumors develop, low-grade glioma (LGG) therapy is often initiated without histologic confirmation of the diagnosis in classic cases. In cases with atypical disease location, older age at presentation or imaging appearance, a biopsy may be considered to exclude higher-grade lesions. METHODS Retrospective chart review, case series RESULTS Four adolescent patients with NF1 presented with atypical suspected gliomas. All four patients underwent surgical biopsy/resection. Case 1 was a left temporal lesion in the previous radiation field for optic pathway glioma; biopsy confirmed LGG with MAP2K1 mutation and increased focal proliferation index (28%), but methylation did not match with any established classification. The patient progressed through multiple rounds of therapy and succumbed to her tumor. Case 2 was a left occipital lesion; biopsy confirmed PA with CDKN2A deletion. The tumor displayed rapid regrowth, but subsequently stabilized. Case 3 was a right frontal lesion; confirmed PA. The tumor demonstrated some regrowth but then stabilized. Case 4 was a basal ganglia lesion; confirmed PA. The patient has demonstrated stable MRI findings and has not required further intervention. CONCLUSIONS Biopsy yielded helpful prognostic information (additional mutations, proliferation rate) in half of these atypical cases. Biopsy should be carefully considered for NF1 patients with atypical presentation or a history of radiation.

EPEN-19. IMPACT OF MOLECULAR SUBTYPING ON PROGNOSIS IN CHILDREN AND ADOLESCENTS WITH SPINAL EPENDYMOMA

Abstract PURPOSE Ependymomas of the spinal cord are rare among children and adolescents, and the individual risk of disease progression is difficult to predict. Recent advances in subtyping the main molecular groups, myxopapillary ependymoma (MPE) and spinal ependymoma (SP-EPN), have successfully identified distinct risk groups among adult patients. This study aims at evaluating the prognostic impact of MPE subtypes A and B in a pediatric cohort. METHODS Eighty-three patients with spinal ependymoma ≤22 years registered in the HIT-MED database between 1992 and 2022 were included. Forty-seven tumors were analyzed regarding global DNA methylation. In six cases, antibodies against HOXB13 and MYCN were used as surrogate markers for the methylation group. Twenty-eight MPE were further classified into subtypes by t-distributed stochastic neighbor embedding (t-SNE) analysis. RESULTS MPE (n=32, 63%) was the most common molecular type followed by SP-EPN (n=17, 33%) and MYCN-amplified ependymoma (n=2, 4%). One case remained molecularly unclear, and one was excluded due to reclassification as anaplastic pilocytic astrocytoma. MPE subtyping identified 18 MPE-A and 9 MPE-B (inconclusive: n=1). 5-year progression-free survival (5y-PFS) did not significantly differ between MPE and SP-EPN (65% vs. 78%, p=0.64). MYCN-amplification was associated with early relapses and with death in one patient. Patients with MPE-B may have a tendency towards superior 5y-PFS compared to MPE-A (86% vs. 56%, p=0.15), irrespective of the use of adjuvant treatment. MPE-A was more frequently disseminated at time of diagnosis (n=6/18) than MPE-B (n=1/8, not evaluable: n=1; p=0.28). CONCLUSION Molecular subtyping of spinal ependymoma in children does not allow to separate patients into distinct risk groups, yet. However, the potentially favorable PFS among patients with MPE-B prompts the consideration of treatment de-intensification for this group. Larger cohorts and further insights into the molecular heterogeneity of these tumors are needed to complete the basis for future clinical decision-making.

ETMR-01. BRAIN STEM TUMORS IN CHILDREN LESS THAN THREE MONTHS: CLINICAL AND RADIOLOGIC FINDINGS OF A RARE DISEASE

Abstract BACKGROUND Brainstem gliomas account for 10-20% of all central nervous system pediatric neoplasms. Brain stem tumors in children less than three months old at diagnosis are extremely rare. Our aim is to study a retrospective cohort to improve the understanding of the disease course and guide patient management. METHODS This is a multicenter retrospective analysis across the European Society for Pediatric Oncology SIOP-E HGG/DIPG Working Group linked centers and included patients with a brainstem tumor diagnosed between 2009 and 2020 and aged less than 3 months at diagnosis. Clinical data was collected, and imaging characteristics were analyzed blindly and independently by two experienced neuroradiologists. RESULTS Five cases (female; n=4) were identified of which no patient received any therapy. The epicenter of 2 tumors was in the medulla oblongata alone and in the medulla oblongata and the pons in 3 cases. For patients with tumor in equal parts in the medulla oblongata and the pons (n=3) the extension at diagnosis involved the spinal cord; for the 2 patients with the tumor epicenter in the medulla oblongata alone (n=2) the extension at diagnosis included the pons (n=2) and the spinal cord (n=1). Biopsy was performed in one patient identifying a pilocytic astrocytoma. Two patients died rapidly. In one patient autopsy revealed a high-grade glioma (case 3). Three survivors showed either spontaneous tumor regression (n=2) or stable disease (n=1). The surviving patients were followed-up for 10, 7, and 0.6 years, respectively. One case had the typical imaging characteristics of a dorsal exophytic low-grade glioma. CONCLUSIONS No patient fulfilled the radiologic criteria defining a high-grade glioma. Central neuroradiological review and biopsy (if feasible) may provide useful information with regards to the patient’s management.

LGG-27. LOWER GRADE GLIOMA (LGG) IN INFANTS. ANALYSIS OF 25 NON-NF1 PATIENTS

Abstract INTRODUCTION Infants constitute approximately 5% of all pediatric LGG. This group is identified as having aggressive course and worse prognosis as compared to older children. No specific therapeutic guidelines are yet available for this specific age group. AIM: Retrospective analysis of infants diagnosed and treated for LGG. METHODOLOGY: 25 patients treated between 2001-2023 were analyzed for: sex, age, tumor location, pathology, treatment and outcome. NF1 patients were excluded. RESULTS There were 13 boys and 12 girls, aged 3 months-11 months, median 6 months. 12 had optic chiasm tumors, 6 of visual pathway, 3 had tumors of posterior fossa, 2 of pineal region and 1 spinal tumor. Pathology was available for 16 children revealing Pilocytic astrocytoma in 9, Pilomyxoid astrocytoma in 6, ganglioglioma in 1. Resection as first line treatment was performed in posterior fossa and spinal locations, in 4 cases of visual tracts tumors. All patients were treated with chemotherapy with a maximum of 6 subsequent episodes in a patient with visual pathway tumor. MEK inhibitors were given to 3 pts (in 2 discontinued due to cardiotoxicity). Radiotherapy was applied in 5 (older than 4 years). Twenty two patients are alive, from 4 months to 22 years 4 months (median 8 years 11 months) from diagnosis. Three patients died (midline tumors) 2 from electrolyte disorders and 1 from radiation related cerebral bleeding with observation time of 3, 10, 9 years. Among children with visual tract tumors 5 are blind, 3 have impaired vision. Five patients with very good response to first line treatment have excellent quality of life. Ten patients are disabled, requiring help in everyday life. CONCLUSIONS The risk of disability or death is highest in infants of all LGG patients, those who respond the first line treatment have very good quality of life.

MODL-11. LOW-GRADE GLIOMA 3D PATIENT-DERIVED ORGANOID PLATFORM AS TRANSFORMATIVE TOOL FOR TUMOR BIOLOGY AND TRANSLATIONAL RESEARCH

Abstract Unlike many high-grade tumors, low-grade glioma (LGG) has faced challenges in advancing scientific and clinical breakthroughs, affected by the limited capacity to develop representative preclinical tumor models. Major barriers to establishing traditional LGG cell culture systems have been cellular senescence and the need to introduce additional genetic modifications to obtain cultured growth. Such LGG models, while extremely valuable, require extensive periods for development and result in clonally selected lines which may not present the complexity of LGG tumor biology. To mitigate such challenges in LGG model development and address the need for three-dimensional tissue cultures, we have successfully generated organoids from fresh tissue specimens obtained from surgical resection. We have demonstrated success of this method on various pediatric brain tumor histologies and have expanded these approaches successfully to LGG. Through such efforts, we have developed 14 LGG tumors’ organoid models as well as other low-grade tumor’s models such as craniopharyngioma, schwannoma, meningioma, optic glioma, and oligodendroglioma. The tissue was processed immediately post-extraction and cultured in media solution on rotating platform. Organoid growth was observed within 1-3 weeks of initiation and tested for growth for up to 3 months. Phenotypic analysis revealed organoid cell composition representing clinical histology. The immune component was preserved in organoids for up to 40 days. MAPK pathway activity, a hallmark marker for KIAA-BRAF fusion positive pilocytic astrocytoma was preserved for up to 4 weeks. Our successful deployment of three-dimensional patient-tissue derived organoids provides for an efficient, simple workflow for the generation of unique and transformative preclinical models for the LGG field. Supported by the Children’s Brain Tumor network’s open science model, 3D organoids will provide investigations with broader resources for LGG tumor biology preclinical testing and support translational studies on behalf of the development of novel clinical trials.

LGG-38. UNRESECTABLE PEDIATRIC LOW-GRADE GLIOMAS OF THE BRAIN: TARGETED THERAPY COMPARED WITH STANDARD CHEMOTHERAPY AS FIRST-LINE TREATMENT

Abstract BACKGROUND Pediatric low-grade gliomas (pLGG) frequently harbor MAPK-pathway mutations that determine poor response to standard chemotherapy (sCt). Targeted agents against BRAF-V600E mutation (MAPK-i) are emerging as molecularly driven treatments. Few studies have compared sCt with MAPK-i. We aimed to compare response and progression-free survival (PFS) of unresectable brain pLGG treated with sCt or MAPK-i. MAPK-i were used in first line or at relapse. METHODS We conducted a single-center observational retrospective study of all brain pLGG consecutively diagnosed and treated at Gaslini Children’s Hospital between January 2008 and December 2021. Treatment was assessed using RAPNO criteria at 6, 12-18 months, and at last follow-up. MRI studies were reviewed by two experienced neuroradiologists. RESULTS Seventy-one patients were enrolled: 66 received sCt and 10 MAPK-i (5 in first line, 5 after sCt failure). All patients who received MAPK-i were BRAF-V600E mutated. Groups were homogeneous for tumor location and dissemination. sCt group was enriched for pilocytic astrocytoma, MAPK-I group for ganglioglioma. sCt patients were younger. SCt lasted 12-18 months, MAPK-i were continuously given. Tumor size reduction was 19.5% at 6 months and 40.5% at 12-18 months for sCt group; 48% at 6 months and 43.5% at 12-18 months for MAPK-i group. SCt determined at least stable disease in 74.2% of patients; 60% of responders reached the best response at 6 months, 40% at 12-18 months. 5y-PFS was 40.3% (median time for progression: 2.5 years). MAPK-i determined at least stable disease in all patients at first evaluation with long-lasting response (median time of follow-up: 5.1 years). CONCLUSIONS In our study sCt was effective in inducing response but prolonged disease control is not always achieved. BRAF-V600E mutated patients upon MAPK-i start gained a rapid disease control with long-lasting response, also if they have been pretreated. Acknowledgement: this study was supported by ARTUCEBA ONLUS.

LGG-48. CLINICAL CHARACTERIZATION OF FGFR-ALTERED, PEDIATRIC LOW-GRADE GLIOMAS

Abstract BACKGROUND Pediatric low-grade glioma (pLGG) is the most common central nervous system tumor of childhood. Most pLGGs are driven by BRAF alterations, but a subset harbor activating mutations or fusions of FGFR1/2/3. Significantly less is known about the biologic activity, clinical course, and response to targeted inhibition of these FGFR-altered gliomas (FGFR pLGG). We sought to define the epidemiologic characteristics, molecular signature, prognostic markers, and clinical course of patients with FGFR pLGG. METHODS We performed a multi-institution, retrospective chart review of pediatric neuro-oncology patients treated at two large, academic cancer centers from 2012 – 2023 with tumor molecular profiling demonstrating any FGFR alteration. RESULTS Sixteen eligible patients were identified; 9 (56%) were female and median age was 12 years of age (range 6 - 18 years). Reported histologies included pilocytic astrocytoma (4), rosette-forming glioneuronal tumor (3), low grade glial/glioneuronal tumor (3), low grade glioma NOS (2), intermediate grade astrocytoma (1), dysembryoblastic neuroepithelial tumor (2), and pilomyxoid astrocytoma (1). FGFR point mutations were seen in 10/16 (62.5%) patients followed by FGFR-TACC1 fusions in 4/16 (25%) patients and two patients with FGFR1 tandem duplication. Metastatic disease was noted at diagnosis in two patients and upfront gross total resection was achieved in four patients. The most common systemic therapy for the remaining patients was Vincristine and/or Carboplatin. All sixteen patients are alive at median follow up of 52 months (range 6 - 198 months). CONCLUSIONS FGFR pLGG represent a distinct subset of tumors with unique biologic properties and clinical activity. Additional studies are needed to investigate this unique patient population to appropriately adapt our therapeutic approach and improve patient outcomes.

Hypothalamic Hemangioma-like Pilocytic Astrocytoma in an Adult Patient: A Systematic Review with a Focus on Differential Diagnosis and Neurological Presentation.

Background: Pilocytic astrocytoma (PCA) are commonly observed as slow-growing noncancerous brain tumors in pediatric populations, but they can also occur in adults, albeit rarely. When located in diencephalic regions, particularly in the hypothalamus, they present unique diagnostic and management challenges due to their rarity and overlapping clinical and radiological features with other intracranial pathologies. This systematic review aims to provide a comprehensive understanding of hypothalamic PCA in adults, focusing on their differential diagnosis, neurological presentation, diagnostic modalities, treatment strategies. A case illustration is also described in order to better underline all the difficulties related to the diagnostic process. Material and methods: A systematic literature search was conducted in the PubMed/MEDLINE, Embase, and Scopus databases up to November 2023 to identify studies. Results: The systematic literature search identified a total of 214 articles. Following screening by title and abstract and full-text review, 12 studies were deemed eligible and are included here. Conclusions: Adult-onset PCA in diencephalic regions pose diagnostic challenges due to their rarity and overlapping features with other intracranial lesions. Advanced imaging techniques play a crucial role in diagnosis, while surgery remains the cornerstone of treatment. Multidisciplinary collaboration is essential for the optimal management and long-term follow-up of these patients.

Intestinal perforation due to a ventriculoperitoneal shunting catheter

Introduction: The ventriculoperitoneal (VP) shunt allows the drainage of excess cerebrospinal fluid; among its gastrointestinal complications are intestinal volvulus, pseudocyst, and perforation, the last of which is rare but potentially serious, with a frequency between 0.1% and 0.7% and a mortality rate around 15%. We present the case of a male child who required VP shunt colocation and suffered GI tract perforation with transanal protrusion. Case report: A three-year-old male with a long clinical history of pilocytic astrocytoma in the posterior fossa that was partially resected in February 2022 and with VP shunt placement since March 2022. He was diagnosed with an intestinal perforation and anal externalization due to a VP shunt. He required surgery and management with combined antimicrobials. Discussion: Although the aetiology of GI tract perforation due to a VP shunt is not fully established, some risk factors have been described, including the use of abdominal trocars, rigid distal catheters, silicone allergies, and children's thin intestine walls. Treatment must be individualized, with some principles including external drainage of the proximal part until the CSF fluid reaches a biochemically near-normal state and becomes sterile on culture; secondly, the administration of intravenous antibiotics; and finally, the removal of the perforating section of the catheter. Conclusions: Bowel perforation due to a VP shunt is an extremely rare entity whose aetiology is not fully established, primarily affects children and may be mostly related to chronic-irritative gastrointestinal distress. Individualizing treatment is the cornerstone of the therapeutic approach that includes VP shunt replacement, antimicrobial therapy, and management of life-threatening complications.

An Overview of Optic Pathway Glioma With Neurofibromatosis Type 1: Pathogenesis, Risk Factors, and Therapeutic Strategies.

Optic pathway gliomas (OPGs) are most predominant pilocytic astrocytomas, which are typically diagnosed within the first decade of life. The majority of affected children with OPGs also present with neurofibromatosis type 1 (NF1), the most common tumor predisposition syndrome. OPGs in individuals with NF1 primarily affect the optic pathway and lead to visual disturbance. However, it is challenging to assess risk in asymptomatic patients without valid biomarkers. On the other hand, for symptomatic patients, there is still no effective treatment to prevent or recover vision loss. Therefore, this review summarizes current knowledge regarding the pathogenesis of NF1-associated OPGs (NF1-OPGs) from preclinical studies to seek potential prognostic markers and therapeutic targets. First, the loss of the NF1 gene activates 3 distinct Ras effector pathways, including the PI3K/AKT/mTOR pathway, the MEK/ERK pathway, and the cAMP pathway, which mediate glioma tumorigenesis. Meanwhile, non-neoplastic cells from the tumor microenvironment (microglia, T cells, neurons, etc.) also contribute to gliomagenesis via various soluble factors. Subsequently, we investigated potential genetic risk factors, molecularly targeted therapies, and neuroprotective strategies for tumor prevention and vision recovery. Last, potential directions and promising preclinical models of NF1-OPGs are presented for further research. On the whole, NF1-OPGs develop as a result of the interaction between glioma cells and the tumor microenvironment. Developing effective treatments require a better understanding of tumor molecular characteristics, as well as multistage interventions targeting both neoplastic cells and non-neoplastic cells.

Solid pilocytic astrocytoma in cavum septum pellucidum: a description of two cases and an analysis of misdiagnosis

Solid pilocytic astrocytoma in cavum septum pellucidum: a description of two cases and an analysis of misdiagnosis

Childhood Posterior Fossa Tumours: Experience from a Tertiary Center in Nepal

Background: Brain tumour is a common problem in paediatric age group and posterior fossa is the commonest location. Treatment of these tumours is difficult due to a confined space and potential involvement of brainstem. The aim of this study is to analyse the clinical features, radiological findings, pathological diagnosis, surgical management, postoperative complications and outcome in 3 months in paediatric patients with posterior fossa tumours. Method: Retrospective chart review of 24 patients treated in the Department of Neurosurgery, TUTH, between 2019 April – 2023 April was done. The variables included were age, sex, clinical features, radiological findings, histopathological diagnosis, management and postoperative complications. Results: Twenty-four patients (30%) out of 80 childhood tumors were located in posterior fossa. The most common presenting symptoms was headache in 83.3% and vomiting in 75%. The most common location of tumour was the fourth ventricle in 66.7% while most common tumour histology was Type IV medulloblastoma in 45%. The commonest mode of treatment in 90% of cases was Ventriculoperitoneal (VP) shunting followed by surgical excision of tumour. Conclusion: Posterior fossa tumours are common tumour occurring in children. Majority of the patients presented with features of raised intracranial pressure and gait ataxia. Fourth ventricle and cerebellar vermis are the most common location. Most common histology types are medulloblastoma followed by pilocytic astrocytoma and ependymoma. Management involves addressing acute hydrocephalus followed by definitive surgery. Keywords: Medulloblastoma, Paediatrics, Posterior fossa, Surgery, Ventriculoperitoneal shunt

P.073 Spontaneous fluctuation of contrast enhancement in adult pilocytic astrocytoma and other low-grade brain tumors

Background: Pilocytic astrocytoma and other circumscribed low-grade brain tumors can exhibit spontaneous enhancement changes despite stable size and clinical status. We aimed to describe this phenomenon in adults. Methods: We performed a retrospective review of our MRI database (2011-2021) to identify cases with enhancement changes in otherwise stable tumors. We searched for reports containing: “pilocytic”, “pilomyxoid”, “RGNT”, “rosette”, “glioneuronal”, “DNET”, and “dysembryoplastic”. Exclusion criteria included WHO grade 3/4 tumors, patients <19 years, equivocal diagnostic findings, and no serial MRIs. We reviewed 238 patients. Results: We identified 12 adult patients with the desired phenomenon: 6 pilocytic astrocytoma, 1 pilomyxoid astrocytoma, 2 rosette-forming glioneuronal tumor, 1 unverified low-grade glioma, and 2 cases without biopsy. Seven were untreated, while five were residual or recurrent tumors. Six showed a pattern of new/increasing and subsequent decreasing/disappearing enhancement over 1-4 years. One exhibited spontaneous regression of enhancement over 1 year. Five showed repeating cycles of increasing and decreasing enhancement over longer monitoring periods of 7-15 years, with mean duration of increasing enhancement prior to decline of 21.4 months (SD 5.9). Conclusions: Spontaneous contrast enhancement fluctuation in adult pilocytic astrocytoma and other circumscribed low-grade brain tumors can occur, and on its own should not be misconstrued as evidence of tumor progression/regression.

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.

Detection of tumor-derived cell-free DNA in cerebrospinal fluid using a clinically validated targeted sequencing panel for pediatric brain tumors.

Clinical sequencing of tumor DNA is necessary to render an integrated diagnosis and select therapy for children with primary central nervous system (CNS) tumors, but neurosurgical biopsy is not without risk. In this study, we describe cell-free DNA (cfDNA) in blood and cerebrospinal fluid (CSF) as sources for "liquid biopsy" in pediatric brain tumors. CSF samples were collected by lumbar puncture, ventriculostomy, or surgery from pediatric patients with CNS tumors. Following extraction, CSF-derived cfDNA was sequenced using UW-OncoPlex™, a clinically validated next-generation sequencing platform. CSF-derived cfDNA results and paired plasma and tumor samples concordance was also evaluated. Seventeen CSF samples were obtained from 15 pediatric patients with primary CNS tumors. Tumor types included medulloblastoma (n = 7), atypical teratoid/rhabdoid tumor (n = 2), diffuse midline glioma with H3 K27 alteration (n = 4), pilocytic astrocytoma (n = 1), and pleomorphic xanthoastrocytoma (n = 1). CSF-derived cfDNA was detected in 9/17 (53%) of samples, and sufficient for sequencing in 8/10 (80%) of extracted samples. All somatic mutations and copy-number variants were also detected in matched tumor tissue, and tumor-derived cfDNA was absent in plasma samples and controls. Tumor-derived cfDNA alterations were detected in the absence of cytological evidence of malignant cells in as little as 200µl of CSF. Several clinically relevant alterations, including a KIAA1549::BRAF fusion were detected. Clinically relevant genomic alterations are detectable using CSF-derived cfDNA across a range of pediatric brain tumors. Next-generation sequencing platforms are capable of producing a high yield of DNA alterations with 100% concordance rate with tissue analysis.