A population-based study of the incidence and survival rates in patients with pilocytic astrocytoma

Evaluation of KIAA1549::BRAF fusions and clinicopathological insights of pilocytic astrocytomas

BACKGROUND

Pilocytic astrocytoma (PAs) represents a significant portion of childhood primary brain tumors, with distinct histological and radiological features. The prevalence of KIAA1549::BRAF fusion in PAs has been well-established, this study aims to assess the prevalence of KIAA1549::BRAF fusions and explore their associations with tumor characteristics, radiological findings, and patient outcomes in PAs.

METHODS

Histologically confirmed cases of PAs from a 5-year period were included in the study. Demographic, histopathological, and radiological data were collected, and immunohistochemistry was performed to characterize tumor markers. FISH and qRT-PCR assays were employed to detect KIAA1549::BRAF fusions. Statistical analyses were conducted to examine associations between fusion status and various other parameters.

RESULTS

Histological analysis revealed no significant differences in tumor features based on fusion status. However, younger age groups showed higher fusion prevalence. Radiologically, fusion-positive cases were distributed across different tumor subtypes SE, CWE and NCWE. Survival analysis did not demonstrate a significant impact of fusion status on overall survival, however most cases with recurrence and death harboured KIAA1549::BRAF fusion. Of 200 PAs, KIAA1549::BRAF fusions were detected in 64 % and 74 % of cases via qRT-PCR and FISH, respectively. Concordance between the two platforms was substantial (86 %).

CONCLUSION

KIAA1549::BRAF fusions are prevalent in PAs and can be reliably detected using both FISH and qRT-PCR assays. Cost considerations suggest qRT-PCR as a more economical option for fusion detection in routine clinical practice.

Spinal cord anaplastic Pilocytic Astrocytoma - two stage resection with elsberg and beer technique. Case report and literature review

Pilocytic Astrocytomas are generally presenting as WHO grade 1 intracranial masses in the paediatric population with a favourable prognostic. In less common instances they can be found in the spinal cord. There have been rare cases of Anaplastic variants of the Cranial Pilocytic Astrocytomas. We report a rare instance of an adult patient with pilocytic astrocytoma of the cervical cord with anaplastic features. Our patient presented with 6 months history of neck pain and right-hand paraesthesia which partially responded to steroid treatment. MRI of the cervical spine demonstrated marked expansion of the cervical cord with oedema extending cranially to the medulla and caudally to the mid-thoracic cord. Post-gadolinium T1-weighted images showed intense intramedullary enhancement mainly centred at the level of the C3 vertebra. Diffusion Tensor Imaging Tractography showed the central location of the tumour expanding the cord and displacing the tracts circumferentially. Surgical resection was performed in two stages according to the Elsberg and Beer technique that assisted with safe margin tumour debulking. The histological sections revealed a glial lineage tumour with retained ATRX nuclear expression, positive for GFAP, Ki-67 estimated to 10% and a methylation class corresponding to an Anaplastic Pilocytic Astrocytoma. Subsequently, our patient underwent adjuvant radiotherapy and chemotherapy (10 cycles of Temozolamide and 6 cycles of CCNU). Symptomatic progression developed at 18 months from the initial surgery, radiological progression at 34 months and the overall survival was 40 months. We reviewed the literature and found only four other cases with similar histology.

"Hemispheric pilocytic astrocytoma" revisited: A comprehensive clinicopathological and molecular series emphasizing their overlap with other glioneuronal tumors

Pilocytic astrocytomas (PA) typically exhibit distinct clinical, radiological, histopathological, and genetic features. DNA-methylation profiling distinguishes PA according to their location (infratentorial, midline, hemispheric, or spinal). In the hemispheric location, distinguishing PA from glioneuronal tumors remains a common diagnostic challenge for neuropathologists. Furthermore, the current version of the DKFZ classifier seems to have difficulty separating them from gangliogliomas. In this study, after central radiological review, we identified a histopathologically defined set of PA (histPA, n = 11) and a cohort of DNA-methylation defined PA (mcPA, n = 11). Nine out of the 11 histPA matched the methylation class of hemispheric PA, whereas 2 cases were classified at the end of the study as dysembryoplastic neuroepithelial tumors. Similarly, the mcPA cohort contained tumors mainly classified as PA (7/11), but 4 cases were classified as glioneuronal. The analysis of the 16 tumors with an integrated diagnosis of PA revealed that they affect mainly children with a wide spectrum of radiological, histopathological (i.e. a predominantly diffuse growth pattern), and genetic characteristics (large range of mitogen-activated protein kinase alterations). Based on these results, we consider hemispheric PA to be different from their counterparts in other locations and to overlap with other glioneuronal tumors, reinforcing the necessity of interpreting all data to obtain an accurate diagnosis.

Magnetic resonance imaging characteristics of pediatric pilocytic astrocytoma

PURPOSE

MRI has an important role in diagnosing pilocytic astrocytoma and post-surgical follow-up since the surgical approach has a leading role in its treatment. The purpose of our study is to provide an overview of the typical and atypical MRI findings in a series of pediatric patients with isolated-not NF1-related-pilocytic astrocytomas and to correlate specific MRI patterns with clinical variables.

METHODS

This is a cross-sectional retrospective study providing the analysis of several clinical and neuroradiological findings from a cohort of pediatric pilocytic astrocytoma, starting from the data collected in the Fondazione IRCCS Istituto Neurologico Carlo Besta (FINCB) internal Cancer Registry during an 11-year time period (January 2008-January 2019).

RESULTS

Fifty-six patients were included in the study. Median age at diagnosis was 9.4 years; a slight female prevalence was noticed (m/f ratio 44.6%/55.4%). The majority of pPAs had well-defined contours: 51 (91.1%), 47 (88.7%) were hypointense on T1-wi, all of them were hyperintense on T2-wi, 46 (90.2%) were hyperintense on FLAIR, and 48 (85.7%) were heterogeneous on T1-wi and T2-wi sequences. We found positive correlation between pPAs location and age (r = 0.017), and small degree of connection between pPAs location and gender (Cramer's V = 0.268).

CONCLUSIONS

We presented typical and atypical pPAs MRI findings. Age and tumor location were positevely correlated, while degree of connection between gender and pPAs location was small. All of this may aid clinicians, most of all neuroradiologists, neurosurgeons, and neurologists in proper diagnoses and follow-up of these specific patient population.

Unraveling the signaling mechanism behind astrocytoma and possible therapeutics strategies: A comprehensive review

BACKGROUND

A form of cancer called astrocytoma can develop in the brain or spinal cord and sometimes causes death. A detailed overview of the precise signaling cascade underlying astrocytoma formation has not yet been revealed, although various factors have been investigated. Therefore, our objective was to unravel and summarize our current understanding of molecular genetics and associated signaling pathways with some possible therapeutic strategies for astrocytoma.

RECENT FINDINGS

In general, four different forms of astrocytoma have been identified in individuals, including circumscribed, diffuse, anaplastic, and multiforme glioblastoma, according to a recent literature review. All types of astrocytoma have a direct connection with some oncogenic signaling cascade. Common signaling is MAPK cascade, including Ras-Raf-ERK, up-regulated with activating EGFR/AKT/PTEN/mTOR and PDGFR. Recent breakthrough studies found that BRAF mutations, including KIAA1549: BRAF and BRAF V600E are responsible for astrocytoma progression. Additionally, cancer progression is influenced by mutations in some tumor suppressor genes, such as the Tp53/ATRX and MGMT mutant. As synthetic medications must cross the blood-brain barrier (BBB), modulating signal systems such as miRNA is the primary option for treating patients with astrocytoma. However, available surgery, radiation therapy, and experimental therapies such as adjuvant therapy, anti-angiogenic therapy, and EGFR-targeting antibody drug are the usual treatment for most types of astrocytoma. Similar to conventional anticancer medications, some phytochemicals slow tumor growth by simultaneously controlling several cellular proteins, including those involved in cell cycle regulation, apoptosis, metastatic spread, tyrosine kinase, growth factor receptor, and antioxidant-related proteins.

CONCLUSION

In conclusion, cellular and molecular signaling is directly associated with the development of astrocytoma, and a combination of conventional and alternative therapies can improve the malignancy of cancer patients.

Pilocytic astrocytoma harboring a novel GNAI3-BRAF fusion

Pilocytic astrocytoma (PA), a central nervous system (CNS) World Health Organization grade 1 tumor, is mainly seen in children or young adults aged 5-19. Surgical resection often provides excellent outcomes, but residual tumors may still remain. This low-grade tumor is well recognized for its classic radiological and morphological features; however, some unique molecular findings have been unveiled by the application of next-generation sequencing (NGS). Among the genetic abnormalities identified in this low-grade tumor, increasing evidence indicates that BRAF alterations, especially BRAF fusions, play an essential role in PA tumorigenesis. Among the several fusion partner genes identified in PAs, KIAA1549-BRAF fusion is notably the most common detectable genetic alteration, especially in the cerebellar PAs. Here, we report a case of a young adult patient with a large, right-sided posterior fossa cerebellar and cerebellopontine angle region mass consistent with a PA. Of note, NGS detected a novel GNAI3-BRAF fusion, which results in an in-frame fusion protein containing the kinase domain of BRAF. This finding expands the knowledge of BRAF fusions in the tumorigenesis of PAs, provides an additional molecular signature for diagnosis, and a target for future therapy.

Clinical Characteristics and Long-term Outcomes of Spinal Pilocytic Astrocytomas: A Multicenter Retrospective Study by the Neurospinal Society of Japan

OBJECTIVE

The characteristics, imaging features, long-term surgical outcomes, and recurrence rates of primary spinal pilocytic astrocytomas (PAs) have not been clarified owing to their rarity and limited reports. Thus, this study aimed to analyze the clinical presentation, radiological features, pathological findings, and long-term outcomes of spinal PAs.

METHODS

Eighteen patients with spinal PAs who were surgically treated between 2009 and 2020 at 58 institutions were included in this retrospective multicenter study. Patient data, including demographics, radiographic features, treatment modalities, and long-term outcomes, were evaluated.

RESULTS

Among the 18 consecutive patients identified, 11 were women and 7 were men; the mean age at presentation was 31 years (3-73 years). Most PAs were located eccentrically, were solid or heterogeneous in appearance (cystic and solid), and had unclear margins. Gross total resection (GTR), subtotal resection (STR), partial resection (PR), and biopsy were performed in 28%, 33%, 33%, and 5% of cases, respectively. During a follow-up period of 65 ± 49 months, 4 patients developed a recurrence; however, the recurrence-free survival did not differ significantly between the GTR and non-GTR (STR, PR, and biopsy) groups.

CONCLUSION

Primary spinal PAs are rare and present as eccentric and intermixed cystic and solid intramedullary cervical tumors. The imaging features of spinal PAs are nonspecific, and a definitive diagnosis requires pathological support. Surgical resection with prevention of neurological deterioration can serve as the first-line treatment; however, the resection rate does not affect recurrence-free survival. Investigation of relevant molecular biomarkers is required to elucidate the regrowth risk and prognostic factors.

Radiosurgery outcomes in infratentorial juvenile pilocytic astrocytomas

PURPOSE

To assess survival and neurological outcomes for patients who underwent primary or salvage stereotactic radiosurgery (SRS) for infratentorial juvenile pilocytic astrocytomas (JPA).

METHODS

Between 1987 and 2022, 44 patients underwent SRS for infratentorial JPA. Twelve patients underwent primary SRS and 32 patients underwent salvage SRS. The median patient age at SRS was 11.6 years (range, 2-84 years). Prior to SRS, 32 patients had symptomatic neurological deficits, with ataxia as the most common symptom in 16 patients. The median tumor volume was 3.22 cc (range, 0.16-26.6 cc) and the median margin dose was 14 Gy (range, 9.6-20 Gy).

RESULTS

The median follow-up was 10.9 years (range, 0.42-26.58 years). Overall survival (OS) after SRS was 97.7% at 1-year, and 92.5% at 5- and 10-years. Progression free survival (PFS) after SRS was 95.4% at 1-year, 79.0% at 5-years, and 61.4% at 10-years. There is not a significant difference in PFS between primary and salvage SRS patients (p = 0.79). Younger age correlated with improved PFS (HR 0.28, 95% CI 0.063-1.29, p = 0.021). Sixteen patients (50%) had symptomatic improvements while 4 patients (15.6%) had delayed onset of new symptoms related to tumor progression (n = 2) or treatment related complications (n = 2). Tumor volumetric regression or disappearance after radiosurgery was found in 24 patients (54.4%). Twelve patients (27.3%) had delayed tumor progression after SRS. Additional management of tumor progression included repeat surgery, repeat SRS, and chemotherapy.

CONCLUSIONS

SRS was a valuable alternative to initial or repeat resection for deep seated infratentorial JPA patients. We found no survival differences between patients who had primary and salvage SRS.

A nine-month-old boy with regression of milestones and severe constipation: an unusual case of a large spinal NTRK1 fusion pilocytic astrocytoma

INTRODUCTION

Pilocytic astrocytoma, a World Health Organization grade 1 tumor, is the most common brain tumor in children between 5 and 14 years of age and the second most common in children younger than 5 and older than 14. Although classical to the cerebellum and hypothalamic regions, it can also arise in the spinal cord. Larotrectinib, a selective inhibitor of tropomyosin receptor kinase, has been effective in pediatric tumors with NTRK fusion mutations in children as young as 1-month-old.

CASE

We share the case of a 9-month-old boy who presented with a 4-month history of regression of his milestones and severe constipation who was found to have a large spinal pilocytic astrocytoma with multiple intracranial periventricular lesions.

The global prevalence of primary central nervous system tumors: a systematic review and meta-analysis

BACKGROUND

Primary central nervous system (CNS) tumors are a heterogeneous group of neoplasms, including benign and malignant tumors. Since there are many heterogeneities in the prevalence reported in previous studies on this type of tumor, this study was performed to determine the overall prevalence of different primary CNS tumors.

METHOD

The study was conducted as a systematic review and meta-analysis by searching international databases, including PubMed, Scopus, Science Direct, Web of science, and the Google Scholar search engine until August 2020. After transferring the studies to information management software (EndNote) and eliminating duplicate studies, the remaining studies were reviewed based on inclusion and exclusion criteria according to three stages of primary and secondary evaluation and qualitative evaluation. Comprehensive Meta-Analysis software, Begg, Mazumdar, and I² tests were used for data analysis, publication bias analysis, and heterogeneity analysis, respectively.

RESULTS

After performing the systematic review steps, 80 studies were included for final analysis. Based on 8 studies, the prevalence of brain tumors was 70.9%. Also, studies on 7 other studies showed that the prevalence of spinal tumors was 12.2%. A review of 14 studies showed that the prevalence of neuroepithelial tumors was 34.7%. The analysis of 27 studies reported a prevalence of glioma tumors of 42.8%. Analyses performed on other studies showed that the prevalence of pituitary adenomas was 12.2%, embryonal tumors 3.1%, ependymal tumors 3.2%, meningiomas 24.1%, glial tumors 0.8%, astrocytic 20.3%, oligodendroglial 3.9%, glioblastoma 17.7%, schwannoma 6.7%, medulloblastoma 7.7% and Polycystic astrocytomas 3.8%.

CONCLUSION

As a result, it can be stated that brain tumors are the most common type of primary CNS tumors. It was also observed that tumors involving neuroepithelial cells are more common in patients than other types of tumors.

Benign Glioma

Benign glioma broadly refers to a heterogeneous group of slow-growing glial tumors with low proliferative rates and a more indolent clinical course. These tumors may also be described as "low-grade" glioma (LGG) and are classified as WHO grade I or II lesions according to the Classification of Tumors of the Central Nervous System (CNS) (Louis et al. in Acta Neuropathol 114:97-109, 2007). Advances in molecular genetics have improved understanding of glioma tumorigenesis, leading to the identification of common mutation profiles with significant treatment and prognostic implications. The most recent WHO 2016 classification system has introduced several notable changes in the way that gliomas are diagnosed, with a new emphasis on molecular features as key factors in differentiation (Wesseling and Capper in Neuropathol Appl Neurobiol 44:139-150, 2018). Benign gliomas have a predilection for younger patients and are among the most frequently diagnosed tumors in children and young adults (Ostrom et al. in Neuro Oncol 22:iv1-iv96, 2020). These tumors can be separated into two clinically distinct subgroups. The first group is of focal, well-circumscribed lesions that notably are not associated with an increased risk of malignant transformation. Primarily diagnosed in pediatric patients, these WHO grade I tumors may be cured with surgical resection alone (Sturm et al. in J Clin Oncol 35:2370-2377, 2017). Recurrence rates are low, and the prognosis for these patients is excellent (Ostrom et al. in Neuro Oncol 22:iv1-iv96, 2020). Diffuse gliomas are WHO grade II lesions with a more infiltrative pattern of growth and high propensity for recurrence. These tumors are primarily diagnosed in young adult patients, and classically present with seizures (Pallud et al. Brain 137:449-462, 2014). The term "benign" is a misnomer in many cases, as the natural history of these tumors is with malignant transformation and recurrence as grade III or grade IV tumors (Jooma et al. in J Neurosurg 14:356-363, 2019). For all LGG, surgery with maximal safe resection is the treatment of choice for both primary and recurrent tumors. The goal of surgery should be for gross total resection (GTR), as complete tumor removal is associated with higher rates of tumor control and seizure freedom. Chemotherapy and radiation therapy (RT), while not typically a component of first-line treatment in most cases, may be employed as adjunctive therapy in high-risk or recurrent tumors and in some select cases. The prognosis of benign gliomas varies widely; non-infiltrative tumor subtypes generally have an excellent prognosis, while diffusely infiltrative tumors, although slow-growing, are eventually fatal (Sturm et al. in J Clin Oncol 35:2370-2377, 2017). This chapter reviews the shared and unique individual features of the benign glioma including diffuse glioma, pilocytic astrocytoma and pilomyxoid astrocytoma (PMA), subependymal giant cell astrocytoma (SEGA), pleomorphic xanthoastrocytoma (PXA), subependymoma (SE), angiocentric glioma (AG), and chordoid glioma (CG). Also discussed is ganglioglioma (GG), a mixed neuronal-glial tumor that represents a notable diagnosis in the differential for other LGG (Wesseling and Capper 2018). Ependymomas of the brain and spinal cord, including major histologic subtypes, are discussed in other chapters.

Spectrum of qualitative and quantitative imaging of pilomyxoid, intermediate pilomyxoid and pilocytic astrocytomas in relation to their genetic alterations

PURPOSE

Pilomyxoid astrocytomas (PMA) are pediatric brain tumors predominantly located in the suprasellar region, third ventricle and posterior fossa, which are considered to be more clinically aggressive than pilocytic astrocytomas (PA). Another entity, intermediate pilomyxoid tumors (IPT), exists within the spectrum of pilocytic/pilomyxoid astrocytomas. The 2021 WHO CNS classification refrained from assigning grade 1 or 2 status to PMA, thereby reflecting the need to further elucidate their clinical and imaging characteristics.

METHODS

We included a total of 15 patients with PMA, IPT and suprasellar PA. We retrospectively evaluated immunohistochemistry, imaging findings and diffusion characteristics within these tumors as well as whole exome sequencing for three of the cases.

RESULTS

87% of the tumors were supratentorial with 11 cases suprasellar in location, 1 case located in the frontal white matter and 1 in the hippocampus. 6 cases demonstrated intraventricular extension. ADC values were higher in PMA and IPT than PA. 3 cases demonstrated KIAA1549-BRAF-fusion, 2 had BRAF[Formula: see text]-mutation and 6 were BRAF-wildtype. All cases had recurrence/progression on follow-up.

CONCLUSION

PMA and IPT do not demonstrate aggressive imaging characteristics in respect to their diffusion imaging with ADC values being higher than PA. Lack of BRAF-alteration in PMA corresponded to atypical location of tumors with atypical driver mutations and mechanisms.

Long-term outcome after management of pilocytic astrocytoma in the posterior fossa in a pediatric population

Background and purpose

To assess the impact of posterior fossa pilocytic astrocytoma (PA) removal in pediatric patients, with special focus on postoperative neurological outcome after repeated surgery for tumor remnants.

Methods

Our institutional database was screened for patients with PA treated between 2000 and 2019. Patients ≤ 18 years of age with complete clinical records, preoperative contrast enhanced magnetic resonance imaging (MRI) and postoperative follow-up time of ≥ 6 months were suitable for study inclusion. Functional outcome was quantified with the modified Ranking Scale (mRS) score and assessed at admission, at discharge and at every follow-up investigation. Predictors of hydrocephalus, cranial nerve deficits and tumor recurrence were evaluated.

Results

A total of 57 pediatric patients with a mean age of 7.7 ± 4.8 years were included in the analysis. 27 (47.3%) children suffered from hydrocephalus at diagnosis, out of which 19 (33.3%) required a subsequent VP-Shunt. 22 (39.3%) patients had a partial resection, of which 9 (40.9%) went through second-look surgery. 2 patients with initially radiological confirmation of complete resection, had a tumor recurrence at FU and needed second-look surgery. Among the children requiring second-look surgery, 7 (63.6%) had a complete resection. Favorable outcome (mRS≤2) after initial and second-look surgery was observed in 52 patients (91.2%). Univariate analysis identified tumor location in the floor of the 4th ventricle (p = 0.030), and repeated surgery for tumor remnant removal (p = 0.043) as predictors for post-operative cranial nerve deficits. Multivariate analysis confirmed this independent association. The incidence of tumor recurrence occurred more often in patients with previous partial resection (p = 0.009) as well as in lesions located in the cerebellar peduncles (p = 0.043). Partial resection remained an independent predictor after multivariate logistic regression analysis (p = 0.045).

Conclusions

Incomplete resection of posterior fossa PA is a risk factor for tumor recurrence and repeated surgery to remove tumor remnants increases the risk of new postoperative deficits. Thus, the risk of iatrogenic deterioration due to second look surgery should be implemented in the primary pre- and intraoperative decision-making.

Endoscopic transnasal surgery in optic pathway gliomas located in the chiasma-hypothalamic region: case series of ten patients in a single-center experience and endoscopic literature review

OBJECTIVE

Optic pathway gliomas (OPGs) constitute approximately 3-5% of childhood intracranial tumors. In this study, the authors presented their experience of using the endoscopic endonasal approach to treat patients with OPG located in the chiasma-hypothalamic region and aimed to use the infrachiasmatic corridor in the endoscopic endonasal approach as an alternative to the transcranial approach in the surgical necessity of OPGs.

METHODS

We retrospectively analyzed the data of ten patients diagnosed with OPG histopathologically among 3757 cases who underwent endoscopic endonasal surgery between August 1997 and March 2021 at Kocaeli University Faculty of Medicine Pituitary Research Center and Department of Neurosurgery. Mean follow-up period 48.5 months. During the postoperative follow-up period, 3 of these 10 patients underwent reoperation due to tumor recurrence. Combined (endoscopic endonasal approach + transcranial approach) approach was applied to 2 patients in the same session. Surgical and clinical outcomes were evaluated in detail.

RESULTS

Ten patients with a mean patient age of 20.6 ± 11.4 were included in this study. The most common complaint was visual impairment. After surgery, improvement in visual impairment was observed in five patients. No increase in postoperative visual impairment was observed in any of the patients. Postoperative panhypopituitarism was not observed in any of the patients. STR resection was performed in 5 patients and NTR resection in 5 patients. No additional treatment was required during follow-up in 4 of 5 patients who underwent NTR. A total of 6 patients received postoperative radiotherapy treatment.

CONCLUSIONS

In gliomas located in the chiasma-hypothalamic region, appropriate patient selection and endoscopic endonasal surgical treatment may contribute to the elimination of symptoms due to the mass effect of the tumor. It may also contribute to keeping the disease under control with targeted adjuvant therapies by clarifying the pathological diagnosis of the lesion.

A High Grade Astrocytoma with Pilocytic Morphology in a 5-Month-Old American Bulldog

Simple Summary

Dogs are valuable models for spontaneous intracranial neoplasia in humans. The most common intracranial neoplasm in dogs is meningioma, followed by glioma and choroid plexus tumors. Pilocytic astrocytoma (PA) is a form of glioma and is a common childhood and adolescent tumor in humans. There have been two previous reports of PA in dogs. These cases were both adult dogs and the clinical and imaging features were not described. This report describes a 23-week-old female intact American Bulldog with a 2-week progressive history of neurologic dysfunction. Magnetic resonance imaging (MRI) revealed a large hemorrhagic mass that was confirmed on post-mortem examination to be a high-grade astrocytoma with pilocytic morphology. This case is the first to report a high-grade astrocytoma with pilocytic morphology in a juvenile dog.

Abstract

A 23-week-old female intact American Bulldog was presented for a two-week history of progressive circling to the right, twitching, and altered mentation. Magnetic resonance imaging (MRI) revealed a non-contrast enhancing hemorrhagic mass centered in the right thalamus with concurrent subdural and intraventricular hemorrhage. Post-mortem histologic examination of the brain confirmed a mass centered on the thalamus with histomorphologic features consistent with a high-grade astrocytoma with pilocytic morphology. To the authors’ knowledge, the present case is the first to report clinical and imaging characteristics of a high-grade astrocytoma with pilocytic morphology in a young dog.

Cervicomedullary Purely Solid, Giant Pilocytic Astrocytoma

Pilocytic astrocytomas are well-circumscribed, predominantly cystic mass lesions that have a discrete mural nodule. Giant, solid pilocytic astrocytoma is uncommon. Its characteristic imaging features are described.

Pilocytic astrocytoma of the optic nerve with intracystic hemorrhage in an adult: illustrative case

BACKGROUND

Optic pathway gliomas are uncommon, accounting for 3–5% of childhood brain tumors, and are mostly classified as pilocytic astrocytomas (PAs). PAs of the optic nerve are particularly rare in adults.

OBSERVATIONS

The authors presented the case of PA of the left optic nerve in a 49-year-old woman along with detailed pathological and molecular analyses and sequential magnetic resonance imaging. The tumor had progressed during 5 years of follow-up along with cyst formation and intracystic hemorrhage; it had a thick capsule and contained xanthochromic fluid. The boundary between tumor and optic nerve was unclear. B-type Raf kinase (BRAF) V600E point mutations or translocations, IDH1-R132H mutations, loss of alpha-thalassemia/mental retardation X-linked, and 1p/19q codeletion were negative.

LESSONS

BRAF alterations in pediatric PAs of the optic nerve are less frequent than those observed in PAs in other lesions; the same molecular pattern was observed in the adult case, without changes in BRAF. Surgical management should be indicated only in cases with severely impaired vision or disfigurement because there is no clear border between the tumor and optic nerve. Further discussion is needed to optimize the treatment for adult optic pathway gliomas, including radiotherapy, chemotherapy, and molecular-targeted therapies, in addition to surgical intervention.

The evolving landscape of pilocytic astrocytoma: a bibliometric analysis of the top-100 most cited publications

BACKGROUND

Pilocytic astrocytomas are the most common low-grade glioma of the central nervous system that typically occurs in children, and much research has been dedicated to characterizing their molecular features and clinical courses. We provide an overview of the current literature through the use of a bibliometric analysis of the top 100 most cited publications discussing pilocytic astrocytomas.

METHODS

We identified the top 100 most cited publications discussing pilocytic astrocytomas. Articles were ranked based on the number of citations. Descriptive statistics and univariate analysis were used to determine any trends or significant differences in the data.

RESULTS

Of the top 100 articles, 50 were basic science (50%), 34 were clinical (34%), and 16 were review (16%). The number of citations ranged from 79 to 921, with 123 being the median. The US had the most first authors and principal authors (n = 53 and n = 54, respectively). Years of publication had a left-skewed distribution and peaked during 2011 with 12 articles published in that year. Sixty percent of basic science articles investigated BRAF/MAPK pathways, while 67.6% of clinical articles focused on evaluating treatment options for pilocytic astrocytomas. Compared to basic science and clinical articles, review articles were published more recently (p < 0.001), had fewer authors (p = 0.025) and were published in journals with higher impact factors (p = 0.022).

CONCLUSION

Research regarding pilocytic astrocytomas has increased over the past three decades. Future directions of research point towards employing targeted therapies and discovering additional cellular pathways contributing to disease pathogenesis.

Rare CNS tumors in adults: a population-based study of ependymomas, pilocytic astrocytomas, medulloblastomas and intracranial germ cell tumors

Background

Ependymomas, pilocytic astrocytomas, medulloblastomas, and intracranial germ cell tumors occur relative frequently in children, but are rare central nervous system (CNS) tumors in adults. In this population-based survey, we established incidence, treatment, and survival patterns for these tumors diagnosed in adult patients (≥18 years) over a 30-year period (1989–2018).

Methods

Data on 1384 ependymomas, 454 pilocytic astrocytomas, 205 medulloblastomas, and 112 intracranial germ cell tumors were obtained from the Netherlands Cancer Registry (NCR) on the basis of a histopathological diagnosis. For each tumor type, age-standardized incidence rates and estimated annual percentage change were calculated. Trends in incidence and main treatment modalities were reported per 5-year periods. Overall survival was calculated using the Kaplan–Meier method, and relative survival rates were estimated using the Pohar-Perme estimator.

Results

Incidence and survival rates remained generally stable for pilocytic astrocytomas, medulloblastomas, and germ cell tumors. Increasing incidence was observed for spinal ependymomas, mostly for myxopapillary ependymomas, and survival improved over time for grade II ependymomas (P < .01). Treatment patterns varied over time with shifting roles for surgery in ependymomas and for chemotherapy and radiation in medulloblastomas and germinomas.

Conclusions

The study provides baseline information for highly needed national and international standard treatment protocols, and thus for further improving patient outcomes in these rare CNS tumors.

Insight about the characteristics and surgical resectability of adult pilocytic astrocytoma: tertiary center experience

Aim: Adult pilocytic astrocytoma is a rare tumor. We aim to contribute to understanding its clinical course and prognosis. Patients & methods: We searched our database for patients older than 18 years with pathology-proven pilocytic astrocytoma. Patients' clinical data were analyzed. Results: Fifteen patients were identified. The median age at diagnosis was 25 years (range: 18-56). Tumors were supratentorial in 47%. Gross-total and near-total resections were achieved in 40%, and sub-total resection in 47%. One (7%) recurrence and no mortality were encountered during a median follow-up of 11 months (range: 1-76). Conclusion: Pilocytic astrocytoma behaves differently in adults compared with pediatrics. It tends to arise in surgically challenging areas where the extent of resection may be limited. Total resection should be the main therapy whenever feasible. The survival rates are good, and recurrence is low.

Intramedullary Spinal Cord Lesions: A Single-Center Experience

Objective: Spinal cord tumors constitute a small part of spinal surgery owing to their rarity. This retrospective study describes their current management.Methods: Forty-eight patients were treated for an intramedullary tumor between 2014 and 2020 at a single institution. Patients’ files were retrospectively studied. We detailed clinical status according to neurological deficit and ambulatory ability using the modified McCormick Scale, radiological features like number of levels, associated syringomyelia, surgical technique with or without intraoperative electrophysiological monitoring, pathological findings, and postoperative outcome.Results: The median age of this population was 43 years, including 5 patients under 18 years. The median delay before first neurosurgical contact was 3 months after the first clinical complaint. Treatment was gross total resection in 43.8%, subtotal resection in 50.0%, and biopsy in 6.2%. A laminectomy was performed for all the patients except 2 operated using the laminoplasty technique. Pathological findings were ependymoma in 43.8%, hemangioblastoma in 20.8%, and pilocytic astrocytoma in 10.4%. Six patients were reoperated for a tumor recurrence less than 2 years after the first surgical resection. One patient was reoperated for a postoperative cervical kyphosis.Conclusion: Intramedullary tumors are still a challenging disease and they are treated by various surgical techniques. They must be managed in a specialized center including a trained surgical, radiological, electrophysiological, and pathological team. Arthrodesis must be discussed before performing extensive laminectomy to avoid postoperative kyphosis.

ADC Histogram Analysis of Pediatric Low-Grade Glioma Treated with Selumetinib: A Report from the Pediatric Brain Tumor Consortium

BACKGROUND AND PURPOSE

Selumetinib is a promising MAP (mitogen-activated protein) kinase (MEK) 1/2 inhibitor treatment for pediatric low-grade gliomas. We hypothesized that MR imaging-derived ADC histogram metrics would be associated with survival and response to treatment with selumetinib.

MATERIALS AND METHODS

Children with recurrent, refractory, or progressive pediatric low-grade gliomas who had World Health Organization grade I pilocytic astrocytoma with KIAA1549-BRAF fusion or the BRAF V600E mutation (stratum 1), neurofibromatosis type 1-associated pediatric low-grade gliomas (stratum 3), or sporadic non-neurofibromatosis type 1 optic pathway and hypothalamic glioma (OPHG) (stratum 4) were treated with selumetinib for up to 2 years. Quantitative ADC histogram metrics were analyzed for total and enhancing tumor volumes at baseline and during treatment.

RESULTS

Each stratum comprised 25 patients. Stratum 1 responders showed lower values of SD of baseline ADC_total as well as a larger decrease with time on treatment in ADC_total mean, mode, and median compared with nonresponders. Stratum 3 responders showed a greater longitudinal decrease in ADC_total. In stratum 4, higher baseline ADC_total skewness and kurtosis were associated with shorter progression-free survival. When all 3 strata were combined, responders showed a greater decrease with time in ADC_total mode and median. Compared with sporadic OPHG, neurofibromatosis type 1-associated OPHG had lower values of ADC_total mean, mode, and median as well as ADC_enhancement mean and median and higher values of ADC_total skewness and kurtosis at baseline. The longitudinal decrease in ADC_total median during treatment was significantly greater in sporadic OPHG compared with neurofibromatosis type 1-associated OPHG.

CONCLUSIONS

ADC histogram metrics are associated with progression-free survival and response to treatment with selumetinib in pediatric low-grade gliomas.

Outcome of Childhood Cerebellar Pilocytic Astrocytoma: A Series With 20 Years of Follow Up

Background: Cerebellar pilocytic astrocytoma (PCA) is one of the few CNS tumors that can be cured with gross-total removal (GTR). In this series, we had 39 patients diagnosed with cerebellar PCA, 27 patients (70%) had GTR, and mean follow-up period was 62 months with no tumor recurrence.

Objective: To assess the long-term outcome of childhood cerebellar PCA treated at our institute during the period 2000-2020 and to highlight our surgical protocol.

Methodology: Retrospective review of all patients under 18 years of age who were diagnosed with cerebellar PCA and had surgical excision between 2000 and 2020 at the Medical City of King Saud University.

Results: The study included 39 patients: 17 males and 22 females, the mean age was 8.4 years. Radiologically, the tumor was solid in eight patients, cystic in 15 patients, and mixed components were found in 16 patients. The lesion was located in the right cerebellar hemisphere in 12 patients, left cerebellar hemisphere in five patients, and midline 22 patients. The tumor size ranged from 2 to 7 cm in its greatest diameter, it was <5 cm in 13 patients and >5 cm in 26 patients. Thirty-one patients had preoperative hydrocephalus. GTR of the tumor was achieved in 27 patients and subtotal resection (STR) was done in 12 patients, 18 patients required permanent ventriculoperitoneal (V-P) shunt, and five patients had postoperative radiotherapy. Postoperative complications included infection in two patients, cerebellar mutism in two patients, and significant neurologic disability in four patients. The duration of follow-up ranged from 0 to 240 months (mean follow-up period: 62.0 months). The outcome at 10 years was good in 30 patients, fair in four patients, poor in four patients, and one patient died. Recurrence was documented in nine patients, seven of them had GTR and two had STR.

Conclusion: GTR, if achievable, is curative for childhood cerebellar PCA. Many posterior fossa surgical complications could be avoided with watertight dural closure. Although new dural substitutes are available we prefer using autologous grafts (pericranium). It is easy to harvest pericranial graft from the external ventricular drain (EVD) site. The insertion of EVD synchronously with GTR of the tumor and gradual weaning of EVD could avoid the insertion of V-P shunt.

Genetic and histopathological associations with outcome in pediatric pilocytic astrocytoma

OBJECTIVE

Pilocytic astrocytomas (PAs) have a generally favorable prognosis; however, progression or recurrence after resection is possible. The prognostic value of histopathological qualifiers (defined below) or BRAF alterations is not well understood. The aim of this study was to identify the prognostic value of genetic and histopathological features of pediatric PAs.

METHODS

Patients treated for a WHO grade I PA at a single institution were analyzed for histopathological and genetic features and outcomes. "Histopathological qualifier" refers to designations such as "WHO grade I PA with increased proliferative index." BRAF alterations include gene fusions and point mutations. Patients with neurofibromatosis type 1 were excluded.

RESULTS

A total of 222 patients were analyzed (51% female, mean age 9.6 years). Tumors were located in the cerebellum/fourth ventricle (51%), optic pathway/hypothalamus (15%), brainstem (12%), and cerebral cortex (11%). BRAF alterations were screened for in 77 patients and identified in 56 (73%). Histopathological qualifiers were present in 27 patients (14%). Resection was performed in 197 patients (89%), 41 (21%) of whom displayed tumor progression or recurrence after resection. Tumor progression or recurrence was not associated with histopathologic qualifiers (p = 0.36) or BRAF alterations (p = 0.77). Ki-67 proliferative indices were not predictive of progression or recurrence (p = 0.94). BRAF alterations, specifically KIAA1549 fusions, were associated with cerebellar/fourth ventricular tumor location (p < 0.0001) and younger patient age (p = 0.03). Patients in whom gross-total resection was achieved had lower rates of progression and recurrence (p < 0.0001).

CONCLUSIONS

Histopathological features/qualifiers and BRAF alterations were not associated with tumor recurrence/progression in pediatric PAs. The extent of resection was the only factor analyzed that predicted outcome.

A fully automatic multiparametric radiomics model for differentiation of adult pilocytic astrocytomas from glioblastomas

OBJECTIVES

To develop a fully automatic radiomics model to differentiate adult pilocytic astrocytomas (PA) from high-grade gliomas (HGGs).

METHODS

This retrospective study included 302 adult patients with PA (n = 62) or HGG (n = 240). The patients were randomly divided into training (n = 211) and test (n = 91) sets. Clinical data were obtained, and radiomic features (n = 372) were extracted from multiparametric MRI with automatic tumour segmentation. After feature selection with F-score, a Light Gradient Boosting Machine classifier with subsampling was trained to develop three models: (1) clinical model, (2) radiomics model, and (3) combined clinical and radiomics model. Human performance was also assessed. The performance of the classifier was validated in the test set. SHapley Additive exPlanations (SHAP) was applied to explore the interpretability of the model.

RESULTS

A total of 15 radiomic features were selected. In the test set, the combined clinical and radiomics model (area under the curve [AUC], 0.93) showed a significantly higher performance than the clinical model (AUC, 0.79, p = 0.037) and had a similar performance to the radiomics model (AUC, 0.92, p = 0.828). The combined clinical and radiomics model also showed a significantly higher performance than humans (AUC, 0.76-0.81, p < 0.05). The model explanation by SHAP suggested that lower intratumoural heterogeneity from T2-weighted images was highly associated with PA diagnosis.

CONCLUSIONS

The fully automatic combined clinical and radiomics model may be helpful for differentiating adult PAs from HGGs.

KEY POINTS

• Differentiating adult PAs from HGGs is challenging because PAs may manifest a large spectrum of imaging presentations, often including aggressive imaging features. • The fully automatic combined clinical and radiomics model showed a significantly higher performance than the clinical model or humans. • The model explanation by SHAP suggested that second-order features from T2-weighted imaging were important in diagnosis and might reflect the underlying pathophysiology that PAs have lesser tissue heterogeneity than HGGs.

Clinical factors and conventional MRI may independently predict progression-free survival and overall survival in adult pilocytic astrocytomas

PURPOSE

Pilocytic astrocytoma (PA) is rare in adults, and only limited knowledge on the clinical course and prognosis has been available. The combination of clinical information and comprehensive imaging parameters could be used for accurate prognostic stratification in adult PA patients. This study was conducted to predict the prognostic factors from clinical information and conventional magnetic resonance imaging (MRI) features in adult PAs.

METHODS

A total of 56 adult PA patients were enrolled in the institutional cohort. Clinical characteristics including age, sex, anaplastic PA, presence of neurofibromatosis type 1, Karnofsky performance status, extent of resection, and postoperative treatment were collected. MRI characteristics including major axis length, tumor location, presence of the typical 'cystic mass with enhancing mural nodule appearance', proportion of enhancing tumor, the proportion of edema, conspicuity of the nonenhancing margin, and presence of a cyst were evaluated. Univariable and multivariable Cox proportional hazard modeling were performed.

RESULTS

The 5-year progression-free survival (PFS) and overall survival (OS) rates were 83.9% and 91.l%, respectively. On univariable analysis, older age, larger proportion of edema, and poor definition of nonenhancing margin were predictors of shorter PFS and OS, respectively (all Ps < .05). On multivariable analysis, older age (hazard ratio [HR] = 1.04, P = .014; HR = 1.14, P = .030) and poor definition of nonenhancing margin (HR = 3.66, P = .027; HR = 24.30, P = .024) were independent variables for shorter PFS and OS, respectively.

CONCLUSION

Age and the margin of the nonenhancing part of the tumor may be useful biomarkers for predicting the outcome in adult PAs.

Clinical characteristics and long-term surgical outcomes of spinal pilocytic astrocytoma: a report of twenty cases

BACKGROUND

Primary spinal pilocytic astrocytoma (PA) is an extremely rare low-grade astrocytoma with unclear natural history. The demographic characteristics, imaging features, and long-term surgical outcomes have not been clarified due to low prevalence and limited reports.

METHODS

A retrospective review within a single institution between 2004 and 2018 of all patients with pathologically proven PA was conducted. Patient data including demographics, radiographic features, treatment modalities, and long-term outcomes were evaluated.

RESULTS

Twenty consecutive patients were identified, and 16 (80%) were male patients, with a mean age at presentation of 29 ± 13 years. The lesion was primarily located in cervical (n = 10, 50%), thoracic (n = 7, 35%), cervico-thoracic junction (n = 2), and lumbar level (n = 1, 5%). The tumor had a mean extension of 4 ± 2 (1-7) vertebral segments. Most PAs were located eccentrically (n = 16, 80%), with most being heterogeneous in appearance (cystic and solid) or purely cystic (n = 14, 70%), and had unclear margins (n = 16, 80%). Eleven patients (55%) had associated syringomyelia. Gross total resection (GTR) was achieved in 11 (55%) patients, and subtotal resection (STR) in 9 (45%). During a mean follow-up of 104 ± 56 months, 2 patients died and recurrence was found in 4 patients (20%), translating to a mean progression-free survival of 21 ± 11 months.

CONCLUSION

Primary spinal PA is a rare entity with acceptable progression-free survival if treated appropriately. Surgical resection may provide reasonable prolongation of survival, and GTR should be achieved if possible. A close follow-up is recommended especially for residual lesions, and a further in-depth investigation of molecular biomarkers is needed to stratify risk and prognostic factors.

Primary intraventricular tumors - Imaging characteristics, post-treatment changes and relapses

Primary intraventricular neoplasms are rare tumors that originate from the ependymal or subependymal, septum pellucidum, choroid plexus and the supporting arachnoid tissue. Knowledge of the common locations of these tumors within the ventricular system, together with key imaging characteristics and presentation age, can significantly narrow the differential diagnosis. In 2016, the WHO reorganized the classification of several primary CNS tumors by combining histopathological and molecular data. This study highlights the imaging characteristics, histopathological and molecular data, treatment strategies and post-treatment changes of primary intraventricular tumors. Molecular-based diagnosis can not only aid in patient stratification and personalized treatment, but it can also provide prognostic and predictive value independent of WHO classification.

Differentiation between supratentorial pilocytic astrocytoma and extraventricular ependymoma using multiparametric MRI

BACKGROUND

The differentiation of supratentorial pilocytic astrocytomas (STPAs) and supratentorial extraventricular ependymomas (STEEs) is clinically pivotal because of distinct therapeutic management and prognosis, which is sometimes challenging to both neuroradiologists and pathologists.

PURPOSE

To explore and compare the conventional and advanced magnetic resonance imaging (MRI) features between STPA and STEE.

MATERIAL AND METHODS

A total of 23 patients with STPAs and 23 patients with STEEs were reviewed in this study. All patients performed conventional MRI, susceptibility-weighted imaging (SWI), and diffusion-weighted imaging (DWI), and 34 patients (17 with STPAs and 17 with STEEs) examined dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI) in addition. Clinical data, conventional MRI features, minimum relative apparent diffusion coefficient ratio (rADC_min), and maximum relative cerebral blood volume ratio (rCBV_max) were compared between the two groups and subgroups. The optimal cutoff values of rADC_min and rCBV_max with sensitivity and specificity were calculated.

RESULTS

STPA manifested similar to STEE as a solid-cystic mass but more frequently presented with a marked enhancing deep nodule (P = 0.02), no peritumoral edema (P = 0.036), higher rADC_min value (2.0 ± 0.5 vs. 0.9 ± 0.2; P < 0.001), and lower rCBV_max value (2.1 ± 0.4 vs. 14.4 ± 5.5; P < 0.001). The cutoff value of >1.39 for rADC_min and ≤ 2.81 for rCBV_max produced a high sensitivity of 95.65% and 100.0%, respectively, and all produced a specificity of 100.0% in differentiating STPAs from STEEs.

CONCLUSION

Multiparametric MRI techniques including conventional MRI, DWI, and DSC-PWI contribute to the differential diagnosis of STPA and STEE.

A diagnostic tree for differentiation of adult pilocytic astrocytomas from high-grade gliomas

BACKGROUND

To develop a diagnostic tree analysis (DTA) model based on demographical information and conventional MRI for differential diagnosis of adult pilocytic astrocytomas (PAs) and high-grade gliomas (HGGs; World Health Organization grade III-IV).

METHODS

A total of 357 adult patients with pathologically confirmed PA (n = 65) and HGGs (n = 292) who underwent conventional MRI were included. The patients were randomly divided into training (n = 250) and validation (n = 107) datasets to assess the diagnostic performance of the DTA model. The DTA model was created using a classification and regression tree algorithm on the basis of demographical and MRI findings.

RESULTS

In the DTA model, tumor location (on cerebellum, brainstem, hypothalamus, optic nerve, or ventricle), cystic mass with mural nodule appearance, presence of infiltrative growth, and major axis (cutoff value, 2.9 cm) were significant predictors for differential diagnosis of adult PAs and HGGs. The AUC, accuracy, sensitivity, and specificity were 0.94 (95% confidence interval 0.86-1.00), 96.2%, 89.5%, and 97.7%, respectively, in the test set. The accuracy of the DTA model was significantly higher than the no-information rate in the test (96.2 % vs 85.0%, P < 0.001) set.

CONCLUSION

The DTA model based on MRI findings may be useful for differential diagnosis of adult PA and HGGs.

Pediatric Spinal Cord Diseases

Spinal cord diseases in pediatric patients are highly variable in terms of presentation, pathology, and prognosis. Not only do they differ with respect to each other but so too with their adult equivalents. Some of the most common diseases are autoimmune (ie, multiple sclerosis, acute disseminated encephalomyelitis, and acute transverse myelitis), congenital (ie, dysraphism with spina bifida, split cord malformation, and tethered cord syndrome), tumor (ie, juvenile pilocytic astrocytoma, ependymoma, and hem-angioblastoma), and vascular (ie, cavernous malformations, arteriovenous malformations, and dural arteriovenous fistulas) in nature. These each require their own niche treatment paradigm and prognosis. Furthermore, presentation of different spinal cord diseases in children can be difficult to discern without epidemiologic and imaging data. Interpretation of these data is crucial to facilitating a timely and accurate diagnosis. Correspondingly, the aim of this review was to highlight the most pertinent features of the most common spinal cord diseases in the pediatric population.

Recurrent adult pilocytic astrocytoma presenting with intraventricular and leptomeningeal spread

Background

Infratentorial pilocytic astrocytomas are uncommon tumors in adulthood but are thought to be prognostically similar to their pediatric counterparts with excellent overall survival following gross total resection. However, given the relative rarity of these tumors, no management guidelines exist for recurrent adult pilocytic astrocytomas (APAs). This lack of consensus is especially problematic for inoperable recurrences or those with aggressive features concerning for malignant transformation.

Case Description

In 2017, a 26-year-old female presented with headaches, nausea, vomiting, and blurry vision. A brain magnetic resonance imaging (MRI) demonstrated a large, well-circumscribed mass within the fourth ventricle causing obstructive hydrocephalus. She underwent near-total resection through a midline suboccipital transtonsillar approach. Pathology demonstrated a World Health Organization Grade 1 pilocytic astrocytoma. Despite initial improvement in her symptoms, she developed worsening headaches and lethargy 10 months after surgery and repeat MRI demonstrated recurrent tumor within the entire ventricular system and the subarachnoid spaces of the left cerebellopontine angle suggesting leptomeningeal spread. Due to the unresectable nature of the recurrence, the patient declined any further intervention and succumbed to her disease 6 months later.

Conclusion

We present the first case of a recurrent APA presenting with intraventricular and leptomeningeal spread. Although thought to be a benign neoplasm, close interval follow-up with serial imaging is of essential, especially in those patients with known residual tumor, to prevent aggressive recurrences such as this.

Temporal, spatial, and genetic constraints contribute to the patterning and penetrance of murine neurofibromatosis-1 optic glioma

BACKGROUND

Brain tumors are the most common solid tumors of childhood, but little is understood about the factors that influence their development. Pediatric low-grade gliomas in particular display unique temporal and spatial localization associated with different genetic mutations (eg, BRAF genomic alterations, mutations in the neurofibromatosis type 1 [NF1] gene) for reasons that remain unclear. NF1 low-grade gliomas typically arise in the optic pathway of young children as optic pathway gliomas (OPGs), likely from a cell of origin that resides within the third ventricular zone (TVZ). However, the factors that contribute to their distinct temporal patterning and penetrance have not been adequately explored.

METHODS

TVZ neuroglial progenitor cells (NPCs) were analyzed over the course of mouse brain development. Progenitors isolated by fluorescence-activated cell sorting (FACS) were assessed for functional and molecular differences. The impact of different germline Nf1 mutations on TVZ NPC properties was analyzed using genetically engineered mice.

RESULTS

We identify 3 individual factors that could each contribute to Nf1 optic glioma temporal patterning and penetrance. First, there are 3 functionally and molecularly distinct populations of mouse TVZ NPCs, one of which ("M" cells) exhibits the highest clonogenic incidence, proliferation, and abundance during embryogenesis. Second, TVZ NPC proliferation dramatically decreases after birth. Third, germline Nf1 mutations differentially increase TVZ NPC proliferation during embryogenesis.

CONCLUSIONS

The unique temporal patterning and penetrance of Nf1 optic glioma reflects the combined effects of TVZ NPC population composition, time-dependent changes in progenitor proliferation, and the differential impact of the germline Nf1 mutation on TVZ NPC expansion.

WDR81 Gene Silencing Can Reduce Exosome Levels in Human U87-MG Glioblastoma Cells

Glioblastoma is a very invasive and prevalent brain tumor that affects 15 in 100,000 persons over the age of 70 years. Studies have shown that the expression of the WD repeat domain 81 (WDR81) gene, which is effective in vesicular transport and inhibition of autophagy, is increased in glioblastoma. The decreased autophagy was found to be related to the increased production of exosomes, which is a major factor in the pathogenesis of glioblastoma. The PI-3kinase complex is a pre-autophagic complex that is highly active in the absence of WDR81. The WDR81 gene, as a negative regulator of PI3K activity, prevents autophagy and increases exosome secretion by preventing the formation of the class III PI3K complex. Therefore, targeted reduction of exosomes can be considered an effective strategy for reducing the pathogenesis of glioblastoma. This study aimed to assess the effect of WDR81 gene silencing with siRNA on exosome levels in a U87-MG cell line. Culturing of U87-MG cells was carried out in Dulbecco's modified Eagle medium (DMEM) containing 5% FBS and 1% penicillin/streptomycin. Thereafter, silencing of WDR81 was performed using WDR81 siRNA, whose gene expression level was determined via real-time qRT-PCR. Cell viability was evaluated using the MTT assay. The exosomes were extracted from a cell culture using the Exocib kit. The size accuracy of the exosomes was confirmed by dynamic light scattering (DLS). Finally, the protein content and RNA of the exosomes were assessed. WDR81 gene expression of siRNA-transfected cells was decreased to 82% after 24 h compared to the non-transfected control cells. The analysis of the exosomes showed that the concentration of exosomes and their RNA and protein content in the siRNA-transfected cells decreased significantly compared to the non-transfected control cells. No considerable difference was observed in cell viability after transfection with either WDR81-specific siRNAs or scrambled control siRNAs. Our findings showed that silencing the WDR81 gene could reduce the level of exosomes in human U87-MG glioblastoma cells. Therefore, the reduced exosome content may be suggested as a new gene therapy strategy for targeted therapy of glioblastoma by increasing autophagy via activation of PI3KIII. However, more studies are needed in this regard.

The utilization of sodium fluorescein in pediatric brain stem gliomas: a case report and review of the literature

INTRODUCTION

A major challenge in the surgical resection of brainstem tumors is distinguishing tumor from normal tissue. One approach for addressing this problem is the use of fluorescent tracers such as sodium fluorescein (NaFl). NaFl disseminates through a disruption in the blood-brain barrier (BBB) and accumulates in the extracellular space of brain tumors. Intraoperative fluorescence microscopy can be performed to identify tumor tissue and avoid damage to adjacent, normal tissue. Here, we present the case of a 16-year-old male who underwent a left retrosigmoid craniotomy with splitting of the tentorium to remove a large exophytic brainstem tumor involving the cerebellar peduncle and with superior extension into the midbrain and thalamus.

OBJECTIVES

The primary objective of this study was to investigate the effectiveness of sodium fluorescein as an intraoperative technique and evaluate its potential benefit for resection of tumors in eloquent regions in the pediatric population. To do so, we focused on a case study approach; however, we also performed a literature review and evaluated different intraoperative fluorescent techniques and their benefits for tumor resection.

METHODS

We performed a literature search using PubMed and Google Scholar by the key words "sodium fluorescein," "brain stem tumor," and "central nervous system neoplasms." Twenty-nine articles including both pediatric and adult populations were selected for analysis and qualitative review.

RESULTS

In this case study, sodium fluorescein helped the surgeons to identify and obtain a gross total resection of a large brainstem tumor. The marker was especially helpful for discerning the inferior pole of the tumor buried inconspicuously in cerebellar tissue. We evaluate different fluorescent tracers, 5-ALA and ICG, and discuss their application and benefits in tumor resection surgery. We present different cases that found sodium fluorescein to be helpful in achieving a gross total resection.

CONCLUSION

The application of sodium fluorescein proved to be a safe and effective technique for the resection of brain stem tumors as shown in this case study. It helped to expose concealed areas and illuminate the tumor capsule. Further studies should test the clinical use of sodium fluorescein on brain stem tumor resection.

Typical Pediatric Brain Tumors Occurring in Adults-Differences in Management and Outcome

Adult brain tumors mostly distinguish themselves from their pediatric counterparts. However, some typical pediatric brain tumors also occur in adults. The aim of this review is to describe the differences between classification, treatment, and outcome of medulloblastoma, pilocytic astrocytoma, and craniopharyngioma in adults and children. Medulloblastoma is a WHO IV posterior fossa tumor, divided into four different molecular subgroups, namely sonic hedgehog (SHH), wingless (WNT), Group 3, and Group 4. They show a different age-specific distribution, creating specific outcome patterns, with a 5-year overall survival of 25–83% in adults and 50–90% in children. Pilocytic astrocytoma, a WHO I tumor, mostly found in the supratentorial brain in adults, occurs in the cerebellum in children. Complete resection improves prognosis, and 5-year overall survival is around 85% in adults and >90% in children. Craniopharyngioma typically occurs in the sellar compartment leading to endocrine or visual field deficits by invasion of the surrounding structures. Treatment aims for a gross total resection in adults, while in children, preservation of the hypothalamus is of paramount importance to ensure endocrine development during puberty. Five-year overall survival is approximately 90%. Most treatment regimens for these tumors stem from pediatric trials and are translated to adults. Treatment is warranted in an interdisciplinary setting specialized in pediatric and adult brain tumors.

Cytokines in Pediatric Pilocytic Astrocytomas: A Clinico-Pathological Study

Pilocytic astrocytomas (PCA) are WHO Grade I tumors with a favorable prognosis. Surgical resection is usually curative. Nonetheless, progressive and/or metastatic disease occurs in 20% of patients. For these patients, treatment options are limited. The role of the immune system in PCA has not previously been reported. We hypothesize that the circulating cytokines contribute to tumorigenicity in PCA. This is an exploratory study with a focus on the identification of circulating cerebrospinal (CSF) cytokines associated with PCA. The primary objective is to demonstrate that CSF cytokines will be differentially expressed in the subset of PCAs that are difficult to treat in comparison to their surgically amendable counterparts. This is a single-institution, retrospective study of prospectively collected data. Patients with a confirmed histological diagnosis of PCA who have simultaneous intraoperative CSF sampling are included. Cerebrospinal fluid samples are subjected to multiplex cytokine profiling. Patient-derived PCA lines from selected patients in the same study cohort are cultured. Their cell culture supernatants are collected and interrogated using the sample multiplex platform as the CSF. A total of 8 patients are recruited. There were two patients with surgically difficult tumors associated with leptomeningeal involvement. Multiplex profiling of the cohort’s CSF samples showed elevated expressions of IFN-γ, IL-2, IL-12p70, IL-1β, IL-4, and TNF-α in these two patients in comparison to the remaining cohort. Next, primary cell lines derived from the same PCA patients demonstrated a similar trend of differential cytokine expression in their cell culture supernatant in vitro. Although our findings are preliminary at this stage, this is the first study in pediatric PCAs that show cytokine expression differences between the two groups of PCA with different clinical behaviors.

Is it a new culprit? "TERT promoter mutation" in an aggressive pediatric pilocytic astrocytoma

Recent advances in the genomic study have revolutionized the discovery of molecular biomarkers in glioma not only to aid in targeted therapy but also to prognosticate character of tumor and outcome of a patient.The usually benign nature of pilocytic astrocytoma (PA) can now be challenged with the discovery of genomic alterations that could promote more aggressive clinical behavior. CDKN2A deletion and ATRX gene inactivation or mutation have been the most common molecular alterations in worse prognosis.We will discuss a case of pilocytic astrocytoma showing the progressive recurrence with pilomyxoid features and the presence of TERT promoter mutation.

Adult pilocytic astrocytoma in the molecular era: a comprehensive review

Adult pilocytic astrocytoma (PA) is less prevalent than pediatric PA and is associated with a worse prognosis. In a literature review, we found that 88.3% of the molecular alterations in adult PA are associated with MAPK pathway dysregulation. The most common alterations are fusions of BRAF. Understanding of the mechanisms underlying this pathway has evolved substantially, heralding advancements in specific targeted therapy. Here, we review clinical and molecular features of adult PA, characteristics predicting aggressive behavior and approaches to standard and investigational therapies. We highlight epigenetic profiling and integrated diagnosis as an essential component of classifying PA.

Treatment with endoscopic transnasal resection of hypothalamic pilocytic astrocytomas: a single-center experience

Backgrounds

Pilocytic astrocytomas (PAs) are World Health Organization (WHO) grade I tumors, which are relatively common, and are benign lesions in children. PAs could originate from the cerebellum, optic pathways, and third ventricular/hypothalamic region. Traditional various transcranial routes are used for hypothalamic PAs (HPAs). However, there are few studies on hypothalamic PAs treated through the endoscopic endonasal approach (EEA). This study reports the preliminary experience of the investigators and results with HPAs via expanded EEAs.

Methods

All patients with HPAs, undergone EEA in our hospital from 2017 to 2019, were retrospectively reviewed. The demographic data, clinical symptoms, complications, skull base reconstruction, prognosis, and endocrinological data were all recorded and analyzed in detail.

Results

Finally, five female patients were enrolled. The average age of patients was 28.6 ± 14.0. All patients had complaints about their menstrual disorder. One patient had severe bilateral visual impairment. Furthermore, only one patient suffered from severe headache due to acute hydrocephalus, although there were four patients with headache or dizziness. Four cases achieved gross-total resection, and one patient achieved subtotal resection. Furthermore, there was visual improvement in one patient (case 5), and postoperative worsening of vision in one patient (case 4). However, only one patient had postoperative intracranial infection. None of the patients experienced a postoperative CSF leak, and in situ bone flap (ISBF) techniques were used for two cases for skull base repair. In particular, ISBF combined with free middle turbinate mucosal flap was used for case 5. After three years of follow-up, three patients are still alive, two patients had no neurological or visual symptoms, or tumor recurrence, and one patient had severe hypothalamic dysfunction. Unfortunately, one patient died of severe postoperative hypothalamus reaction, which presented with coma, high fever, diabetes insipidus, hypernatremia and intracranial infection. The other patient died of recurrent severe pancreatitis at one year after the operation.

Conclusion

Although the data is still very limited and preliminary, EEA provides a direct approach to HPAs with acceptable prognosis in terms of tumor resection, endocrinological and visual outcomes. ISBF technique is safe and reliable for skull base reconstruction.

Chemotherapy-induced changes in tumor consistency can allow gross total resection of previously unresectable brainstem pilocytic astrocytoma

Background

Low-grade gliomas (LGG) are described by the World Health Organization as Grades I and II. Among LGGs, the most common primary brain tumor is pilocytic astrocytoma (PA) and carries an excellent prognosis when treated with complete surgical resection. Cases, in which this is not possible, are associated with less favorable outcomes and worse progression-free survival.

Case Description

This report describes a case of a 22-year-old male, who presented with progression of a primary brainstem tumor previously treated with stereotactic radiosurgery and chemotherapy. Patient underwent surgical exploration and was diagnosed with juvenile PA, but debulking was limited by the very dense and fibrous tumor. Complete surgical resection was not possible at this time. Despite efforts to treat with chemotherapy, the patient presented a year later with clinical deterioration and severe neurologic deficits, prompting surgical re-exploration. During the second operation, the tumor was found to have undergone very significant softening in consistency, allowing for gross total resection (GTR).

Conclusion

Aggressive treatment of brainstem LGG should be pursued whenever possible, given its generally favorable prognosis. Repeat microsurgical resection, even with a different approach, might be reasonable and safe. Finally, chemotherapy may be associated with changes in the tumor consistency that can render previously unresectable lesions amenable to successful aggressive resection.

NF-кB inhibition by DHMEQ: in vitro antiproliferative effects on pilocytic astrocytoma and concise review of the current literature

INTRODUCTION

Pilocytic astrocytoma (PA) is the most common brain tumor that affects the pediatric population. Even though PA is benign and treatment only involves surgery, recurrent or unresectable tumors require chemo- and radiotherapy. Besides BRAF, CDKN2A, or IDH mutations, the hyperactivation of the nuclear factor NF-κB contributes to tumor growth and survival.

METHODS

In the present study, we used publicly available data for the in silico analysis of NF-κB subunits (RELA, RELB, REL, NF-κB1, and NF-κB2) expression in PA samples. Besides, in vitro assays were performed to evaluate proliferation, migration, cell death, on the PA cell line Res286 comparing to human primary astrocytes. Sensitization to radiation therapy and temozolomide (TMZ) was also assayed.

RESULTS

Our results showed that all the members of the NF-kB family are upregulated in PA datasets compared to normal brain tissues. Moreover, DHMEQ treatment significantly reduced cell growth and motility, while sensitized cells to ionizing radiation and TMZ, as previously seen in high-grade gliomas.

CONCLUSIONS

This drug presents a potential application in clinical practice for the treatment of recurrent or inoperable PA. Moreover, its use might assist adjuvant chemotherapy and reduce irradiation doses to avoid toxicity to the surrounding tissues.

Reappraisal of haemorrhagic suprasellar pilocytic astrocytoma during adulthood

Pilocytic astrocytomas comprise the most common central nervous system tumour during childhood and have an excellent response to surgical treatment in this population. The tumour incidence decreases with age, whereas more aggressive behaviour tends to increase. Haemorrhage as a presenting feature of pilocytic astrocytomas is a rare phenomenon, especially in the adult population. We present a case of a 55-year-old patient with progressive headaches and dizziness. MRI confirmed a sellar and predominantly retrochiasmal suprasellar lesion with heterogeneous signal, enhancement and blood products. Management via transsphenoidal approach was performed, and histopathology revealed the unexpected diagnosis of haemorrhagic pilocytic astrocytoma. Haemorrhagic pilocytic astrocytoma is an infrequent entity in the adult population and it is essential to recognise the peculiarities regarding diagnostic evaluation and management, which differ from the paediatric population. During adulthood, this tumour carries an overall unfavourable prognosis, with higher rates of progression and recurrence.

Intraoperative MRI-guided Resection in Pediatric Brain Tumor Surgery: A Meta-analysis of Extent of Resection and Safety Outcomes

BACKGROUND

 The objective of this meta-analysis was to analyze the impact of intraoperative magnetic resonance imaging (iMRI) on pediatric brain tumor surgery with regard to the frequency of histopathologic entities, additional resections secondary to iMRI, rate of gross total resections (GTR) in glioma surgery, extent of resection (EoR) in supra- and infratentorial compartment, surgical site infections (SSIs), and neurologic outcome after surgery.

METHODS

 MEDLINE/PubMed Service was searched for the terms "intraoperative MRI," "pediatric," "brain," "tumor," "glioma," and "surgery." The review produced 126 potential publications; 11 fulfilled the inclusion criteria, including 584 patients treated with iMRI-guided resections. Studies reporting about patients <18 years, setup of iMRI, surgical workflow, and extent of resection of iMRI-guided glioma resections were included.

RESULTS

 IMRI-guided surgery is mainly used for pediatric low-grade gliomas. The mean rate of GTR in low- and high-grade gliomas was 78.5% (207/254; 95% confidence interval [CI]: 64.6-89.7, p < 0.001). The mean rate of GTR in iMRI-assisted low-grade glioma surgery was 74.3% (35/47; 95% CI: 61.1-85.5, p = 0.759). The rate of SSI in surgery assisted by iMRI was 1.6% (6/482; 95% CI: 0.7-2.9). New onset of transient postoperative neurologic deficits were observed in 37 (33.0%) of 112 patients.

CONCLUSION

 IMRI-guided surgery seems to improve the EoR in pediatric glioma surgery. The rate of SSI and the frequency of new neurologic deficits after IMRI-guided surgery are within the normal range of pediatric neuro-oncologic surgery.

The Search for Molecular Markers in a Gene-Orphan Case Study of a Pediatric Spinal Cord Pilocytic Astrocytoma

BACKGROUND/AIM

We herein presented a case of pediatric spinal cord pilocytic astrocytoma diagnosed on the basis of histopathological and clinical findings.

MATERIALS AND METHODS

Given the paucity of data on genetic features for this tumor, we performed exome, array CGH and RNA sequencing analysis from nucleic acids isolated from a unique and not repeatable very small amount of a formalin-fixed, paraffin-embedded (FFPE) specimen.

RESULTS

DNA mutation analysis, comparing tumor and normal lymphocyte peripheral DNA, evidenced few tumor-specific single nucleotide variants in DEFB119, MUC5B, NUDT1, LTBP3 and CPSF3L genes. Differently, tumor DNA was not characterized by for the main pilocytic astrocytoma gene variations, including BRAFV600E. An inframe trinucleotides insertion involving DLX6 or lnc DLX6-AS1 genes was scored in 44.9% of sequenced reads; the temporal profile of this variation on the expression of DLX-AS1 was investigated in patient's urine-derived exosomes, reporting no significant variation in the one-year molecular follow-up. Array CGH identified a tumor microdeletion at the 6q25.3 chromosomal region, spanning 1,01 Mb and comprising ZDHHC14, SNX9, TULP4 and SYTL3 genes. The expression of these genes did not change in urine-derived exosomes during the one-year investigation period. Finally, RNAseq did not reveal any of the common pilocytic BRAF-KIAA1549 genes fusion events.

CONCLUSION

To our knowledge, the present report is one of the first described gene-orphan case studies of a pediatric spinal cord pilocytic astrocytoma.

Intracranial calcifications in childhood: Part 2

This article is the second of a two-part series on intracranial calcification in childhood. In Part 1, the authors discussed the main differences between physiological and pathological intracranial calcification. They also outlined histological intracranial calcification characteristics and how these can be detected across different neuroimaging modalities. Part 1 emphasized the importance of age at presentation and intracranial calcification location and proposed a comprehensive neuroimaging approach toward the differential diagnosis of the causes of intracranial calcification. Pathological intracranial calcification can be divided into infectious, congenital, endocrine/metabolic, vascular, and neoplastic. In Part 2, the chief focus is on discussing endocrine/metabolic, vascular, and neoplastic intracranial calcification etiologies of intracranial calcification. Endocrine/metabolic diseases causing intracranial calcification are mainly from parathyroid and thyroid dysfunction and inborn errors of metabolism, such as mitochondrial disorders (MELAS, or mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes; Kearns-Sayre; and Cockayne syndromes), interferonopathies (Aicardi-Goutières syndrome), and lysosomal disorders (Krabbe disease). Specific noninfectious causes of intracranial calcification that mimic TORCH (toxoplasmosis, other [syphilis, varicella-zoster, parvovirus B19], rubella, cytomegalovirus, and herpes) infections are known as pseudo-TORCH. Cavernous malformations, arteriovenous malformations, arteriovenous fistulas, and chronic venous hypertension are also known causes of intracranial calcification. Other vascular-related causes of intracranial calcification include early atherosclerosis presentation (children with risk factors such as hyperhomocysteinemia, familial hypercholesterolemia, and others), healed hematoma, radiotherapy treatment, old infarct, and disorders of the microvasculature such as COL4A1- and COL4A2-related diseases. Intracranial calcification is also seen in several pediatric brain tumors. Clinical and familial information such as age at presentation, maternal exposure to teratogens including viruses, and association with chromosomal abnormalities, pathogenic genes, and postnatal infections facilitates narrowing the differential diagnosis of the multiple causes of intracranial calcification.

Demographics of Astrocytoma in Central Texas: The Interaction Between Race, Histology, and Primary Tumor Site

Introduction The epidemiological factors surrounding astrocytoma and gliomas have been studied with little avail. Even limited conclusions have not been reached in spite of significant past research efforts. Ionizing radiation is currently one of the only factors consistently associated with glioma formation. Studies in an attempt to link environmental and occupational exposures with brain neoplasms have continued to produce inconsistent results. This study aims to explore the distribution and epidemiology of astrocytomas within a Central Texas patient population in order to elucidate any possible differences in epidemiologic and prognostic factors based on race, histology, and primary tumor site. Methods Eight hundred forty-five clinical cases with the diagnosis of astrocytoma were retrospectively obtained from the tumor registry of the Scott & White Integrated Healthcare System from 1976 to 2014. We investigated the effects of gender, race, tumor histology, tumor site, treatment methods, and mortality of this cohort of patients in Central Texas. Results Prevalence data echoes that of the national epidemiology in that among our sample, White individuals had the highest prevalence (n=666, 78.8%), followed by Hispanics (n=94, 11.1%) and Black individuals (n=78, 9.2%). White patients had higher rates of parietal lobe (6.6% vs. 0.6%, p<0.01), brain overlapping (6.8% vs. 0.0%, p<0.01), and brainstem (5.9% vs. 1.7%, p=0.02) tumors. Black patients had higher rates of tumors located in brain (not otherwise specified) (35.9% vs. 15.7%, p<0.01) and cerebellum (33.3% vs. 5.6%, p<0.01). Hispanic patients had higher rates of tumor located in the temporal lobe (31.9% vs. 22.8%, p<0.05) and brain (not otherwise specified) (28.7% vs. 16.1%, p<0.01). Hispanics had the largest proportion of deaths (72.3% vs. 38.0%, p<0.01) when compared to the remainder of the sample, followed by White individuals (39.6% vs. 49.7%, p=0.02) and Black individuals (21.8% vs. 43.8%, p<0.01). Conclusions Discrepancies in mortality rates amongst various racial groups may be due to a number of factors. Primary tumor site and histology seem to indeed play a role in mortality and may present variably between ethnic groups. Mortality is also influenced by race, genetic predisposition, environmental and occupational exposure, and access to healthcare.

A Cell-Based MAPK Reporter Assay Reveals Synergistic MAPK Pathway Activity Suppression by MAPK Inhibitor Combination in BRAF-Driven Pediatric Low-Grade Glioma Cells

Pilocytic astrocytomas as well as other pediatric low-grade gliomas (pLGG) exhibit genetic events leading to aberrant activation of the MAPK pathway. The most common alterations are KIAA1549:BRAF fusions and BRAF^V600E and NF1 mutations. Novel drugs targeting the MAPK pathway (MAPKi) are prime candidates for the treatment of these single-pathway diseases. We aimed to develop an assay suitable for preclinical testing of MAPKi in pLGGs with the goal to identify novel MAPK pathway-suppressing synergistic drug combinations. A reporter plasmid (pDIPZ) with a MAPK-responsive ELK-1-binding element driving the expression of destabilized firefly luciferase was generated and packaged using a lentiviral vector system. Pediatric glioma cell lines with a BRAF fusion (DKFZ-BT66) and a BRAF^V600E mutation (BT-40) background, respectively, were stably transfected. Modulation of the MAPK pathway activity by MAPKi was measured using the luciferase reporter and validated by detection of phosphorylated protein levels. A screening of a MAPKi library was performed, and synergy of selected combinations was calculated. Screening of a MAPKi library revealed MEK inhibitors as the class inhibiting the pathway with the lowest IC₅₀s, followed by ERK and next-generation RAF inhibitors. Combination treatments with different MAPKi classes showed synergistic effects in BRAF fusion as well as BRAF^V600E mutation backgrounds. Here, we report a novel reporter assay for medium- to high-throughput preclinical drug testing in pLGG cell lines. The assay confirmed MEK, ERK, and next-generation RAF inhibitors as potential treatment approaches for KIAA1549:BRAF and BRAF^V600E-mutated pLGGs. In addition, the assay revealed that combination treatments synergistically suppressed MAPK pathway activity.

Pediatric Low-Grade Gliomas

Brain tumors constitute the largest source of oncologic mortality in children and low-grade gliomas are among most common pediatric central nervous system tumors. Pediatric low-grade gliomas differ from their counterparts in the adult population in their histopathology, genetics, and standard of care. Over the past decade, an increasingly detailed understanding of the molecular and genetic characteristics of pediatric brain tumors led to tailored therapy directed by integrated phenotypic and genotypic parameters and the availability of an increasing array of molecular-directed therapies. Advances in neuroimaging, conformal radiation therapy, and conventional chemotherapy further improved treatment outcomes. This article reviews the current classification of pediatric low-grade gliomas, their histopathologic and radiographic features, state-of-the-art surgical and adjuvant therapies, and emerging therapies currently under study in clinical trials.