Anaplastic ganglioglioma - a diagnosis comprising several distinct tumour types

Imaging of pediatric glioneuronal and neuronal tumors

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

Ganglioglioma with anaplastic/high-grade transformation: Histopathologic, molecular, and epigenetic characterization of 3 cases

Ganglioglioma (GG) with anaplasia (anaplastic ganglioglioma) is a rare and controversial diagnosis. When present, anaplasia involves the glial component of the tumor, either at presentation or at recurrence. To date, most published cases lack molecular characterization. We describe the histologic and molecular features of 3 patients presenting with BRAF p. V600E-mutant GG (CNS WHO grade 1) with high-grade glial transformation at recurrence. The tumors occurred in pediatric patients (age 9-16 years) with time to recurrence from 20 months to 7 years. At presentation, each tumor was low-grade, with a BRAFV600E-positive ganglion cell component and a glial component resembling pleomorphic xanthoastrocytoma (PXA) or fibrillary astrocytoma. At recurrence, tumors resembled anaplastic PXA or high-grade astrocytomas without neuronal differentiation. CDKN2A homozygous deletion (HD) was absent in all primary tumors. At recurrence, 2 cases acquired CDKN2A HD; the third case showed loss of p16 and MTAP immunoexpression, but no CDKN2A/B HD or mutation was identified. By DNA methylation profiling, all primary and recurrent tumors either grouped or definitely matched to different methylation classes. Our findings indicate that malignant progression of the glial component can occur in GG and suggest that CDKN2A/B inactivation plays a significant role in this process.

DistSNE: Distributed computing and online visualization of DNA methylation-based central nervous system tumor classification

The current state-of-the-art analysis of central nervous system (CNS) tumors through DNA methylation profiling relies on the tumor classifier developed by Capper and colleagues, which centrally harnesses DNA methylation data provided by users. Here, we present a distributed-computing-based approach for CNS tumor classification that achieves a comparable performance to centralized systems while safeguarding privacy. We utilize the t-distributed neighborhood embedding (t-SNE) model for dimensionality reduction and visualization of tumor classification results in two-dimensional graphs in a distributed approach across multiple sites (DistSNE). DistSNE provides an intuitive web interface (https://gin-tsne.med.uni-giessen.de) for user-friendly local data management and federated methylome-based tumor classification calculations for multiple collaborators in a DataSHIELD environment. The freely accessible web interface supports convenient data upload, result review, and summary report generation. Importantly, increasing sample size as achieved through distributed access to additional datasets allows DistSNE to improve cluster analysis and enhance predictive power. Collectively, DistSNE enables a simple and fast classification of CNS tumors using large-scale methylation data from distributed sources, while maintaining the privacy and allowing easy and flexible network expansion to other institutes. This approach holds great potential for advancing human brain tumor classification and fostering collaborative precision medicine in neuro-oncology.

Neuropil-like islands are a possible pathogenetic link between glioblastoma and gangliocytoma/ganglioglioma in a case of synchronous bilateral brain tumors

Neuropil-like islands (NIs) are a histologic hallmark of glioneuronal tumors with neuropil-like islands (GTNIs), but GTNIs are presently not considered a homogeneous entity. The essence of GTNI is likely its glial component, and NIs are now considered aberrant neuronal differentiation or metaplasia. The case we report herein is a 41-year-old woman who was synchronously affected by two brain tumors: one was a glioblastoma (glioblastoma multiforme, GBM), of isocitrate dehydrogenase (IDH)-wild type, with NIs in the left parietal lobe, and the other was histologically a composite gangliocytoma (GC)/anaplastic ganglioglioma (GG) with NIs in the right medial temporal lobe. While both tumors were genetically wild type for IDH, histone H3, and v-raf murine sarcoma viral oncogene homolog B1 (BRAF), the former tumor, but not the latter, was mutated for telomerase reverse transcriptase promoter gene (TERT). A recent systematic study using DNA methylation profiling and next-generation sequencing showed that anaplastic GG separate into other WHO tumor types, including IDH-wild-type GBM. It suggested a diagnostic scheme where an anaplastic GG is likely an IDH-wild-type GBM if it is a BRAF wild type, IDH wild type, and TERT promoter mutant tumor. The likely scenario in this patient is that the GBM results from the progression of GC/anaplastic GG due to the superimposed TERT promoter mutation and the propagation of newly generated GBM cells in the contralateral hemisphere. A systematic analysis using DNA methylation profiling and next-generation sequencing was not available in this study, but the common presence of NIs histologically noted in the two tumors could support this scenario. Although a sufficient volume of molecular and genetic testing is sine qua non for the accurate understanding of brain tumors, the importance of histologic observation cannot be overemphasized.

"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.

A new subtype of diffuse midline glioma, H3 K27 and BRAF/FGFR1 co-altered: a clinico-radiological and histomolecular characterisation

Diffuse midline gliomas (DMG) H3 K27-altered are incurable grade 4 gliomas and represent a major challenge in neuro-oncology. This tumour type is now classified in four subtypes by the 2021 edition of the WHO Classification of the Central Nervous System (CNS) tumours. However, the H3.3-K27M subgroup still appears clinically and molecularly heterogeneous. Recent publications reported that rare patients presenting a co-occurrence of H3.3K27M with BRAF or FGFR1 alterations tended to have a better prognosis. To better study the role of these co-driver alterations, we assembled a large paediatric and adult cohort of 29 tumours H3K27-altered with co-occurring activating mutation in BRAF or FGFR1 as well as 31 previous cases from the literature. We performed a comprehensive histological, radiological, genomic, transcriptomic and DNA methylation analysis. Interestingly, unsupervised t-distributed Stochastic Neighbour Embedding (tSNE) analysis of DNA methylation profiles regrouped BRAFV600E and all but one FGFR1MUT DMG in a unique methylation cluster, distinct from the other DMG subgroups and also from ganglioglioma (GG) or high-grade astrocytoma with piloid features (HGAP). This new DMG subtype harbours atypical radiological and histopathological profiles with calcification and/or a solid tumour component both for BRAFV600E and FGFR1MUT cases. The analyses of a H3.3-K27M BRAFV600E tumour at diagnosis and corresponding in vitro cellular model showed that mutation in H3-3A was the first event in the oncogenesis. Contrary to other DMG, these tumours occur more frequently in the thalamus (70% for BRAFV600E and 58% for FGFR1MUT) and patients have a longer overall survival with a median above three years. In conclusion, DMG, H3 K27 and BRAF/FGFR1 co-altered represent a new subtype of DMG with distinct genotype/phenotype characteristics, which deserve further attention with respect to trial interpretation and patient management.

Brain Tumors in Adolescents and Young Adults: A Review

Brain tumors account for the majority of cancer-related deaths in adolescents and young adults (AYAs), defined as individuals aged 15 to 39. AYAs constitute a distinct population in which both pediatric- and adult-type central nervous system (CNS) tumors can be observed. Clinical manifestations vary depending on tumor location and often include headaches, seizures, focal neurological deficits, and signs of increased intracranial pressure. With the publication of the updated World Health Organization CNS tumor classification in 2021, diagnoses have been redefined to emphasize key molecular alterations. Gliomas represent the majority of malignant brain tumors in this age group. Glioneuronal and neuronal tumors are associated with longstanding refractory epilepsy. The classification of ependymomas and medulloblastomas has been refined, enabling better identification of low-risk tumors that could benefit from treatment de-escalation strategies. Owing to their midline location, germ cell tumors often present with oculomotor and visual alterations as well as endocrinopathies. The management of CNS tumors in AYA is often extrapolated from pediatric and adult guidelines, and generally consists of a combination of surgical resection, radiation therapy, and systemic therapy. Ongoing research is investigating multiple agents targeting molecular alterations, including isocitrate dehydrogenase inhibitors, SHH pathway inhibitors, and BRAF inhibitors. AYA patients with CNS tumors should be managed by multidisciplinary teams and counselled regarding fertility preservation, psychosocial comorbidities, and risks of long-term comorbidities. There is a need for further efforts to design clinical trials targeting CNS tumors in the AYA population.

Primary spinal intramedullary anaplastic ganglioglioma in a pediatric patient

Background

Gangliogliomas (GGs) are rare tumors of the central nervous system composed of neoplastic neural and glial cells and are typically low-grade. Intramedullary spinal anaplastic GGs (AGG) are rare, poorly understood, and often aggressive tumors that can result in widespread progression along the craniospinal axis. Due to the rarity of these tumors, data are lacking to guide clinical and pathologic diagnosis and standard of care treatment. Here, we present a case of pediatric spinal AGG to provide information on our institutional approach to work-up and to highlight unique molecular pathology.

Case Description

A 13-year-old female presented with signs of spinal cord compression including right sided hyperreflexia, weakness, and enuresis. Magnetic resonance imaging (MRI) revealed a C3-C5 cystic and solid mass which was treated surgically with osteoplastic laminoplasty and tumor resection. Histopathologic diagnosis was consistent with AGG, and molecular testing identified mutations in H3F3A (K27M), TP53, and NF1. She received adjuvant radiation therapy and her neurological symptoms improved. However, at 6-month follow-up, she developed new symptoms. MRI revealed metastatic recurrence of tumor with leptomeningeal and intracranial spread.

Conclusion

Primary spinal AGGs are rare tumors, but a growing body of literature shows some trends that may improve diagnosis and management. These tumors generally present in adolescence and early adulthood with motor/sensory impairment and other spinal cord symptoms. They are most commonly treated by surgical resection but frequently recur due to their aggressive nature. Further reports of these primary spinal AGGs along with characterization of their molecular profile will be important in developing more effective treatments.