Bithalamic gliomas may be molecularly distinct from their unilateral high-grade counterparts

Molecular and Pathological Features of Paediatric High-Grade Gliomas

Paediatric high-grade gliomas are among the most common malignancies found in children. Despite morphological similarities to their adult counterparts, there are profound biological and molecular differences. Furthermore, and thanks to molecular biology, the diagnostic pathology of paediatric high-grade gliomas has experimented a dramatic shift towards molecular classification, with important prognostic implications, as is appropriately reflected in both the current WHO Classification of Tumours of the Central Nervous System and the WHO Classification of Paediatric Tumours. Emphasis is placed on histone 3, IDH1, and IDH2 alterations, and on Receptor of Tyrosine Kinase fusions. In this review we present the current diagnostic categories from the diagnostic pathology perspective including molecular features.

Novel therapeutic approaches for pediatric diencephalic tumors: improving functional outcomes

Pediatric diencephalic tumors represent a histopathologically and molecularly diverse group of neoplasms arising in the central part of the brain and involving eloquent structures, including the hypothalamic-pituitary axis (HPA), optic pathway, thalamus, and pineal gland. Presenting symptoms can include significant neurological, endocrine, or visual manifestations which may be exacerbated by injudicious intervention. Upfront multidisciplinary assessment and coordinated management is crucial from the outset to ensure best short- and long-term functional outcomes. In this review we discuss the clinical and pathological features of the neoplastic entities arising in this location, and their management. We emphasize a clear move towards 'function preserving' diagnostic and therapeutic approaches with novel toxicity-sparing strategies, including targeted therapies.

Extra-neural metastases in pediatric diffuse midline gliomas, H3 K27-altered: presentation of two cases and literature review

Introduction

Pediatric diffuse midline gliomas (DMG), H3 K27- altered, are the most aggressive pediatric central nervous system (CNS) malignancies. Disease outcome is dismal with a median survival of less than one year. Extra-neural metastases are an unusual occurrence in DMG and have been rarely described.

Methods and results

Here, we report on two pediatric patients affected by DMG with extra-neural dissemination. Their clinical, imaging, and molecular characteristics are reported here. An 11-year-old male 5 months after the diagnosis of diffuse intrinsic pontine glioma (DIPG) developed metastatic osseous lesions confirmed with computed tomography (CT) guided biopsy of the left iliac bone. The patient died one month after the evidence of metastatic progression. Another 11-year-old female was diagnosed with a cerebellar H3K27- altered DMG. After six months, she developed diffuse sclerotic osseous lesions. A CT-guided biopsy of the right iliac bone was non-diagnostic. She further developed multifocal chest and abdominal lymphadenopathy and pleural effusions. Droplet digital polymerase chain reaction (ddPCR) on pleural effusion revealed the presence of H3.3A mutation (c.83A>T, p.K28M). The patient died 24 months after the diagnosis of DMG and 3 months after the evidence of metastatic pleural effusion.

Discussion

Extra-neural metastasis of DMG is a rare event and no standard therapy exists. An accurate and early diagnosis is necessary in order to develop a personalized plan of treatment. Further research is needed to gain further insights into the molecular pathology of DMG, H3K27- altered and improve the quality of life and the final outcome of patients with this deadly disease.

Spotlights on adult patients with pediatric-type diffuse gliomas in accordance with the 2021 WHO classification of CNS tumors

Introduction

The fifth edition of the World Health Organization (WHO) classification of central nervous system (CNS) tumors released in 2021 formally defines pediatric-type diffuse gliomas. However, there is still little understanding of pediatric-type diffuse gliomas, and even less attention has been paid to adult patients. Therefore, this study describes the clinical radiological, survival, and molecular features of adult patients with pediatric-type glioma.

Methods

Adult patients who underwent surgery from January 2011 to January 2022, classified as pediatric-type glioma, were included in this study. Clinical, radiological, histopathological, molecular pathological, and survival data were collected for analysis.

Results

Among 596 adult patients, 20 patients with pediatric-type glioma were screened, including 6 with diffuse astrocytoma, MYB- or MYBL1-altered, 2 with diffuse midline glioma, H3 K27-altered, and 12 with diffuse pediatric-type high-grade glioma, H3-wildtype and IDH-wildtype. Pediatric high-grade glioma (pHGG) frequently showed tumor enhancement, peritumoral edema, and intratumoral necrosis. Adult patients with pHGG showed a longer life expectancy than adult patients with glioblastoma. Common molecular alterations included chromosome alterations and CDKN2A/B, PIK3CA, and PTEN, while altered KMT5B and MET were found to affect the overall survival.

Conclusion

Our study demonstrated adult patients with pediatric-type glioma. Notably, our research aims to expand the current understanding of adult patients with pediatric-type diffuse gliomas. Furthermore, personalized therapies consisting of targeted molecular inhibitors for MET and VEGFA may exhibit beneficial effects in the corresponding population.

The Role of Epigenetics in Brain and Spinal Cord Tumors

Identification of distinct genetic and epigenetic profiles in various neuroepithelial tumors has improved the classification and uncovered novel diagnostic, prognostic, and predictive molecular biomarkers for improved prediction of treatment response and outcome. Especially, in pediatric high-grade brain tumors, such as diffuse midline glioma, H3K27M-altered and posterior fossa group A-ependymoma, epigenetic changes predominate, along with changes in expression of known oncogenes and tumor suppressor genes induced by histone modifications and DNA methylation. The precise role of epigenetic abnormalities is important for understanding tumorigenesis and the establishment of brain tumor treatment strategies. Using powerful epigenetic-based therapies for cancer cells, the aberrantly regulated epigenome can be restored to a more normal state through epigenetic reprogramming. Combinations of agents targeting DNA methylation and/or other epigenetic modifications may be a promising cancer treatment. Therefore, the integration of multi-omics data including epigenomics is now important for classifying primary brain tumors and predicting their biological behavior. Recent advances in molecular genetics and epigenetic integrated diagnostics of brain tumors influence new strategies for targeted therapy.

Molecular Biomarker Testing for the Diagnosis of Diffuse Gliomas

CONTEXT.—

The diagnosis and clinical management of patients with diffuse gliomas (DGs) have evolved rapidly over the past decade with the emergence of molecular biomarkers that are used to classify, stratify risk, and predict treatment response for optimal clinical care.

OBJECTIVE.—

To develop evidence-based recommendations for informing molecular biomarker testing for pediatric and adult patients with DGs and provide guidance for appropriate laboratory test and biomarker selection for optimal diagnosis, risk stratification, and prediction.

DESIGN.—

The College of American Pathologists convened an expert panel to perform a systematic review of the literature and develop recommendations. A systematic review of literature was conducted to address the overarching question, "What ancillary tests are needed to classify DGs and sufficiently inform the clinical management of patients?" Recommendations were derived from quality of evidence, open comment feedback, and expert panel consensus.

RESULTS.—

Thirteen recommendations and 3 good practice statements were established to guide pathologists and treating physicians on the most appropriate methods and molecular biomarkers to include in laboratory testing to inform clinical management of patients with DGs.

CONCLUSIONS.—

Evidence-based incorporation of laboratory results from molecular biomarker testing into integrated diagnoses of DGs provides reproducible and clinically meaningful information for patient management.

Adult H3K27M mutated thalamic glioma patients display a better prognosis than unmutated patients

BACKGROUND

Adult thalamic gliomas are a rare entity whose management is challenging for physicians. The aim of this study is to describe the characteristics and prognostic factors of thalamic gliomas in adult patients.

METHODS

We retrospectively analyzed the clinical, neuro-radiological, histological, and molecular characteristics of all cases of adult thalamic glioma in our regional center.

RESULTS

We included 38 adult patients. Median age at diagnosis was 56.5 years old (range, 24-80). Median KPS at diagnosis was 70%. Two-thirds of patients presented with tumor necrosis on MRI. Bithalamic lesions were present in four patients. The median volume of enhancement associated with lesions was relatively small (14 mm³). Two patients had undergone partial surgical resection. All other patients underwent biopsy. Median PFS was 7.1 months (95% CI [3.7-10.5]) and median OS was 15.6 months (95% CI [11.7-19.6]). Among 20 patients with available tumor samples for molecular analyses, only 4 (20%) presented with H3K27M mutation. Patients with H3K27M mutation had longer survival compared to those without. Finally, we identified a long-term survivor population characterized by a younger age, no cognitive impairment, low steroid dose treatment and the presence of H3K27M mutation.

CONCLUSION

Thalamic adult glioma differs from bithalamic glioma in children with regards to its clinical, radiological and molecular profiles. Long-term survival is observed in young patients with limited symptoms and H3K27M mutation. A larger prospective cohort is needed to validate these findings.

Topographic correlates of driver mutations and endogenous gene expression in pediatric diffuse midline gliomas and hemispheric high-grade gliomas

We evaluate the topographic distribution of diffuse midline gliomas and hemispheric high-grade gliomas in children with respect to their normal gene expression patterns and pathologic driver mutation patterns. We identified 19 pediatric patients with diffuse midline or high-grade glioma with preoperative MRI from tumor board review. 7 of these had 500 gene panel mutation testing, 11 patients had 50 gene panel mutation testing and one 343 gene panel testing from a separate institution were included as validation set. Tumor imaging features and gene expression patterns were analyzed using Allen Brain Atlas. Twelve patients had diffuse midline gliomas and seven had hemispheric high-grade gliomas. Three diffuse midline gliomas had the K27M mutation in the tail of histone H3 protein. All patients undergoing 500 gene panel testing had additional mutations, the most common being in ACVR1, PPM1D, and p53. Hemispheric high-grade gliomas had either TP53 or IDH1 mutation and diffuse midline gliomas had H3 K27M-mutation. Gene expression analysis in normal brains demonstrated that genes mutated in diffuse midline gliomas had higher expression along midline structures as compared to the cerebral hemispheres. Our study suggests that topographic location of pediatric diffuse midline gliomas and hemispheric high-grade gliomas correlates with driver mutations of tumor to the endogenous gene expression in that location. This correlation suggests that cellular state that is required for increased gene expression predisposes that location to mutations and defines the driver mutations within tumors that arise from that region.

Copy Number Variation and Rearrangements Assessment in Cancer: Comparison of Droplet Digital PCR with the Current Approaches

The cytogenetic and molecular assessment of deletions, amplifications and rearrangements are key aspects in the diagnosis and therapy of cancer. Not only the initial evaluation and classification of the disease, but also the follow-up of the tumor rely on these laboratory approaches. The therapeutic choice can be guided by the results of the laboratory testing. Genetic deletions and/or amplifications directly affect the susceptibility or the resistance to specific therapies. In an era of personalized medicine, the correct and reliable molecular characterization of the disease, also during the therapeutic path, acquires a pivotal role. Molecular assays like multiplex ligation-dependent probe amplification and droplet digital PCR represent exceptional tools for a sensitive and reliable detection of genetic alterations and deserve a role in molecular oncology. In this manuscript we provide a technical comparison of these two approaches with the golden standard represented by fluorescence in situ hybridization. We also describe some relevant targets currently evaluated with these techniques in solid and hematologic tumors.

A Unique Case of Bilateral Thalamic High-Grade Glioma in a Pediatric Patient with LI-Fraumeni Syndrome: Case Presentation and Review of the Literature

Li-Fraumeni syndrome (LFS) is a rare high-penetrance and autosomal-dominant pathological condition caused by the germline mutation of the TP53 gene, predisposing to the development of tumors from pediatric age. We conducted a qualitative systematic review following the ENTREQ (Enhancing Transparency in Reporting the Synthesis of Qualitative Research) framework. A search was made in MEDLINE/Pubmed and MeSH Database using the terms "Li-Fraumeni" AND "pediatric high-grade glioma (HGG)", identifying six cases of HGGs in pediatric patients with LFS. We added a further case with peculiar features such as no familiar history of LFS, association of embryonal rhabdomyosarcoma and bithalamic HGG, whose immunohistochemical profile was accurately defined by Next Generation Sequencing. Knowledge synthesis and case analysis grounded the discussion about challenges in the management of this pathology in pediatric age.

MRI-based diagnosis and treatment of pediatric brain tumors: is tissue sample always needed?

Traditional management of newly diagnosed pediatric brain tumors (PBTs) consists of cranial imaging, typically magnetic resonance imaging (MRI), and is frequently followed by tissue diagnosis, through either surgical biopsy or tumor resection. Therapy regimes are typically dependent on histological diagnosis. To date, many treatment regimens are based on molecular biology. The scope of this article is to discuss the role of diagnosis and further treatment of PBTs based solely on MRI features, in light of the latest treatment protocols. Typical MRI findings and indications for surgical biopsy of these lesions are described.

Pediatric bithalamic gliomas have a distinct epigenetic signature and frequent EGFR exon 20 insertions resulting in potential sensitivity to targeted kinase inhibition

Brain tumors are the most common solid tumors of childhood, and the genetic drivers and optimal therapeutic strategies for many of the different subtypes remain unknown. Here, we identify that bithalamic gliomas harbor frequent mutations in the EGFR oncogene, only rare histone H3 mutation (in contrast to their unilateral counterparts), and a distinct genome-wide DNA methylation profile compared to all other glioma subtypes studied to date. These EGFR mutations are either small in-frame insertions within exon 20 (intracellular tyrosine kinase domain) or missense mutations within exon 7 (extracellular ligand-binding domain) that occur in the absence of accompanying gene amplification. We find these EGFR mutations are oncogenic in primary astrocyte models and confer sensitivity to specific tyrosine kinase inhibitors dependent on location within the kinase domain or extracellular domain. We initiated treatment with targeted kinase inhibitors in four children whose tumors harbor EGFR mutations with encouraging results. This study identifies a promising genomically-tailored therapeutic strategy for bithalamic gliomas, a lethal and genetically distinct brain tumor of childhood.

Surgical treatment and survival outcome of patients with adult thalamic glioma: a single institution experience of 8 years

PURPOSE

Given the rarity in the population with adult thalamic gliomas (ATGs), comprehensive characteristics, treatments and survival outcome are not well characterized. This study was conducted to investigate the comprehensive characteristic and treatment of ATGs and identify the prognostic factors associated with overall survival (OS).

METHODS

A retrospective analysis of newly diagnosed ATGs who underwent surgical resection consecutively was conducted. Survival analysis of OS was performed by Kaplan-Meier analysis. Cox proportional hazard model was used to investigate the possible prognostic factors associated with OS.

RESULTS

A total of 102 patients with ATG were enrolled in this study. The median age was 41 years (range 18-68 years). There were 56 (54.9%) males. Sixty-two patients (60.8%) had glioblastoma (GBM). Among these patients, 46 patients (45.1%) had GTR/NTR, 50 patients (49.0%) had STR and 6 patients (5.9%) had PR. Postoperatively, 71.6% of these patients received adjuvant therapy. The median OS was 13.6 months (range 1 week-75 months). COX regression analysis revealed that ATG patients with longer duration of symptoms (p = 0.024), better pre-KPS (p = 0.045), maximal resection (p = 0.013), or lower tumor grade (p = 0.002) had longer OS, and these predictors are considered as independent prognostic factors. Survival analysis showed that ATGs with GTR/NTR plus chemoradiotherapy had significant OS advantage compared with other treatment regimens.

CONCLUSIONS

This study comprehensively summarized the characteristics, treatments and survival outcomes of ATGs in the largest sample size. Maximal surgical resection can bring survival benefit. Combined-modality therapy regimen of GTR/NTR plus chemoradiotherapy may be better beneficial for OS than other regimens.

Pulvinar Locus is Highly Relevant to Patients' Outcomes in Surgically Resected Thalamic Gliomas in Children

OBJECTIVE

Thalamic gliomas in children are less suitable for surgical resection because of their location. In cases of unavoidable resection, careful surgical planning in addition to histology and extent of resection affects prognosis.

METHODS

A cohort of 10 pediatric patients with thalamic glioma underwent surgical resection at our department. The predominant location of tumor origins in the thalamus was defined in imaging studies. Histopathology was determined (retrospectively in a subset) according to the World Health Organization classification 2016, including the newly established type of "diffuse midline glioma, H3 K27M-mutant."

RESULTS

Three low-grade gliomas (grade I/II) and 7 high-grade gliomas (grade III/IV) were identified. The mean follow-up period was 49.8 months. All 3 low-grade gliomas did not recur (progression-free survival, 58.3 months). Six of 7 high-grade gliomas recurred, and the patients died of the primary disease (overall survival, 28.1 months). Poor outcomes, especially when located at the pulvinar region, were noticeable, with strong predictive power for poor prognosis (P = 0.0018). The presence of H3 K27M mutation and pulvinar location were closely associated (P = 0.0036). Four of 5 patients with pulvinar region tumors developed dissemination and died of the primary disease.

CONCLUSIONS

Pulvinar location is specifically associated with a high rate of malignancy in histology, the presence of H3 K27M mutation, and dissemination at an early disease stage. This association suggests that a distinct biological profile affects prognosis depending on location within the thalamus, especially the pulvinar. We report that tumor location is highly relevant to prognosis and should be taken into consideration when planning treatment.

The molecular oncology of bilateral high-grade thalamic astrocytomas in children

BACKGROUND

Bilateral thalamic astrocytomas in children are exceedingly rare. These highly malignant tumors seldom respond to conventional treatment strategies and carry a grim prognosis for patients. However, recent advances in molecular oncology have had a positive impact on prognostication and treatment strategies of these tumors.

CASE-BASED REVIEW

We present a new case of WHO grade III bilateral thalamic astrocytoma in a child and review the pathophysiology, molecular oncogenesis, and relevant treatment strategies for this rare disease.

CONCLUSIONS

High-grade thalamic astrocytomas affecting both thalami pose a challenge to pediatric neurosurgeons, neuro-oncologists, and neuropathologists given the lack of effective treatment strategies. Understanding recent revelations in the field of molecular oncology can assist clinicians in adequately formulating a treatment plan in this patient population.

Pediatric Thalamic Gliomas: An Updated Review

CONTEXT

- Neoplasms originating in the thalamus are rare overall (1% of all brain tumors); however, they comprise approximately 5% of pediatric intracranial tumors and approach 15% of all malignant pediatric intracranial tumors in some series.

OBJECTIVE

- To update readers about the current understanding of the diverse histology, biology, and behavior of pediatric thalamic tumors. Histologic verification is now thought to be critical for planning treatment, and, as a result, biopsy and total/subtotal resections are much more common today than in the past.

DATA SOURCES

- A PubMed search using the keywords "pediatric + thalamic + glioma" yielded 45 publications with a total of 445 cases of thalamic gliomas in patients less than 18 years of age. We found only 9 substantial institutional series tabulating all encountered thalamic histologic types in children. This survey confirmed a high proportion of astrocytomas, 81% (214 of 265), of which approximately two-thirds were diffuse astrocytomas (146 of 214) and one-third were pilocytic astrocytomas (68 of 214). Of the diffuse astrocytomas, 34% (49 of 146) were low grade (World Health Organization grade II) and 55% (81 of 146) were high grade (World Health Organization grade III or IV), making the latter subgroup the largest single category of all pediatric thalamic tumors. Oligodendrogliomas and ependymomas (mostly anaplastic in both cases) comprised 10% and 3% of all pediatric thalamic tumors, respectively.

CONCLUSIONS

- Tissue diagnosis is now thought crucial for prognostication and treatment, particularly as more potentially therapeutic molecular targets are discovered. Secure diagnosis allows identification of tumors for which resection is more feasible and beneficial.

Identification and targeting of an FGFR fusion in a pediatric thalamic "central oligodendroglioma"

Approximately 1–5% of pediatric intracranial tumors originate in the thalamus. While great strides have been made to identify consistent molecular markers in adult oligodendrogliomas, such as the 1p/19q co-deletion, it is widely recognized that pediatric oligodendrogliomas have a vastly different molecular make-up. While pediatric thalamic or “central oligodendrogliomas” are histologically similar to peripheral pediatric oligodendrogliomas, they are behaviorally distinct and likely represent a cohesive, but entirely different entity. We describe a case of a 10-year-old girl who was diagnosed with an anaplastic glioma with features consistent with the aggressive entity often diagnosed as central or thalamic oligodendroglioma. We performed whole-exome (paired tumor and germline DNA) and transcriptome (tumor RNA) sequencing, which demonstrated an FGFR3-PHGDH fusion. We describe this fusion and our rationale for pursuing personalized, targeted therapy for the patient’s tumor that may potentially play a role in the treatment of similar cases.