Brainstem astroblastoma with MN1 translocation

Posterior fossa astroblastoma: a case report of an extremely rare tumor with challenging diagnosis in a child and a review of literature

A 7-year-old boy presented to the hospital with recurrent nausea and vomiting over 2 weeks. A cranial MRI revealed a large heterogeneous lesion in the posterior fossa extending from the fourth ventricle to the foramen magnum with contact to the brainstem. The lesion showed moderate diffusion restriction and multiple small cystic components. The child underwent gross total resection. The primary histological findings suggested proliferative active tumor without further definition. The extended histological examination 3 weeks later confirmed the diagnosis of astroblastoma. Due to complete resection and full recovery of the patient, watchful waiting with radiological follow-up was recommended. Astroblastoma is an extremely rare tumor especially in the posterior fossa. However, it should be considered as a differential diagnosis in every tumor presenting the discussed radiological and histological features, especially in young aged patients.

Clinicopathological and molecular characterization of astrocytoma

Introduction

Astrocytoma is a rare tumour of the central nervous system that often manifests with non-specific clinical symptoms and lacks distinct histological features. There is a pressing need for further understanding of the clinicopathological and molecular characteristics of astrocytoma. Identifying mutant genes can aid in reliable and early diagnosis, as well as provide insights for the development of targeted therapies.

Methods

This study aims to investigate the clinicopathologic and molecular characteristics of astroblastoma. A total of four patients diagnosed with astroblastoma were included in the analysis. Clinical features, histological findings, and immunohistochemistry results were reviewed and analyzed. Genetic alterations were identified using fluorescence in situ hybridization (FISH) and next-generation sequencing (NGS), followed by patient follow-up.

Results

The study included four female patients, ranging in age from 8 to 44 years. One patient had a tumour in the right parietal lobe, while the other three had tumours in the spinal cord. Histology is usually characterized by pseudorosettes of astroblasts and hyalinization of blood vessels. These tumors showed a growth pattern similar to traditional intracranial astroblastoma, and the histological manifestations of the four patients were all high-grade, showing features of high-density areas of tumor cells or necrosis. Immunohistochemical staining revealed that all four patients expressed OLIG2, EMA, and vimentin, while three patients also expressed GFAP and S-100. The Ki-67 positivity index was approximately 15% in three cases and 10% in one case. Fluorescence in situ hybridization (FISH) using break-apart probes showed EWRS1 breaks in three patients and MN1 breaks in one. Further DNA or RNA-targeted biallelic sequencing identified an EWSR1(Exon1-7)-BEND2(Exon2-14) fusion in case 1, and an EWSR1(Exon1-7)-BEND2(Intergenic) fusion in case 2. In case 3, an EWSR1(Exon1-7)-NUDT10(Intergenic) fusion was present, and in case 4, an MN1(Exon1)-BEND2(Exon2) fusion was identified. The EWSR1-NUDT10 gene fusion is a new fusion type in astroblastoma. The patients were followed up for 76.5, 17.6, 33.7, and 61.3 months, respectively. Three cases experienced tumour recurrences at the spinal cord site, with multiple recurrences in case 4.

Discussion

Our study unveiled the distinctive clinicopathological and molecular mutational characteristics of astrocytoma, while also identifying rare mutated genes. Additionally, the detection of MN1 or EWSR1 gene fusion through FISH or next-generation sequencing can provide valuable insights into the molecular mechanisms and aid in the differential diagnosis of astrocytoma.

MicroRNAs Expression Profile in MN1-Altered Astroblastoma

BACKGROUND/OBJECTIVES

Astroblastoma is a rare glial neoplasm more frequent in young female patients, with unclear clinical behaviors and outcomes. The diagnostic molecular alteration is a rearrangement of the Meningioma 1 (MN1) gene. MicroRNAs (miRNAs) are important gene expression regulators with strong implications in biological processes. Here, we investigated microRNA expression, regulation, and biological processes correlated to target genes of deregulated miRNAs in MN1-altered astroblastoma.

METHODS

A cohort of 14 tumor samples, histologically classified as astroblastoma, was retrospectively collected and analyzed through their DNA methylation profiles. MiRNA expression profiles were then detected on MN1-altered astroblastomas (n = 8) and normal brain controls (n = 2) by Nanostring technology and validated by RT-qPCR; then, the expression of deregulated miRNAs was correlated with clinical-pathological characteristics. Subsequently, the methylation status of promoters of deregulated miRNAs was investigated through a methylation profiling microarray. Finally, bioinformatics analysis was conducted to explore the biological processes (BPs) and target genes of differentially expressed miRNAs.

RESULTS

Eight MN-altered astroblastoma were identified. Thirty-nine miRNAs were deregulated in tumor samples compared to normal brain tissue. Downregulated microRNAs exhibited an association with an increased risk of recurrence. The promoter methylation status was investigated in 32/39 miRNAs: 14/32 were epigenetically deregulated. None of them were genetically regulated.

CONCLUSIONS

MN1-altered astroblastomas have an miRNA expression signature that identifies specific BPs and pathways. Our findings suggested that the involved pathways could be associated with clinical and pathological characteristics of MN1-altered astroblastomas. Also, the biology of this rare tumor could have potential implications on prognostic markers and therapy.

A Radiologist's Guide to the 2021 WHO Central Nervous System Tumor Classification: Part 2-Newly Described and Revised Tumor Types

The fifth edition of the World Health Organization classification of tumors of the central nervous system (CNS), published in 2021, introduces major shifts in the classification of brain and spine tumors. These changes were necessitated by rapidly increasing knowledge of CNS tumor biology and therapies, much of which is based on molecular methods in tumor diagnosis. The growing complexity of CNS tumor genetics has required reorganization of tumor groups and acknowledgment of new tumor entities. For radiologists interpreting neuroimaging studies, proficiency with these updates is critical in providing excellent patient care. This review will focus on new or revised CNS tumor types and subtypes, beyond infiltrating glioma (described in part 1 of this series), with an emphasis on imaging features.

Adult Brainstem Astroblastoma: Unusual Presentation of a Rare Tumor

Astroblastoma is a rare tumor, which is mostly found in pediatric population. Due to scarcity of literature, the data about treatment is lacking. We are reporting case of brainstem astroblastoma in an adult female. A 45-year-old lady presented with complaint of headache, vertigo, vomiting, and nasal regurgitation for 3 months. On examination, she had weak gag, left hemiparesis. Magnetic resonance imaging brain reported medulla oblongata mass, dorsally exophytic. She underwent suboccipital craniotomy and decompression of mass. Histopathology confirmed diagnosis of astroblastoma. She underwent radiotherapy and recovered well. Brainstem astroblastoma is an extremely rare entity. The surgical resection is possible due to well-defined plane. For best outcome, maximum resection and radiation are indicated.

Early ependymal tumor with MN1-BEND2 fusion: a mostly cerebral tumor of female children with a good prognosis that is distinct from classical astroblastoma

PURPOSE

Review of the clinicopathologic and genetic features of early ependymal tumor with MN1-BEND2 fusion (EET MN1-BEND2), classical astroblastomas, and recently described related pediatric CNS tumors. I also briefly review general mechanisms of gene expression silencing by DNA methylation and chromatin remodeling, and genomic DNA methylation profiling as a powerful new tool for CNS tumor classification.

METHODS

Literature review and illustration of tumor histopathologic features and prenatal gene expression timelines.

RESULTS

Astroblastoma, originally descried by Bailey and Cushing in 1926, has been an enigmatic tumor. Whether they are of ependymal or astrocytic derivation was argued for decades. Recent genetic evidence supports existence of both ependymal and astrocytic astroblastoma-like tumors. Studies have shown that tumors exhibiting astroblastoma-like histology can be classified into discrete entities based on their genomic DNA methylation profiles, gene expression, and in some cases, the presence of unique gene fusions. One such tumor, EET MN1-BEND2 occurs mostly in female children, and has an overall very good prognosis with surgical management. It contains a gene fusion comprised of portions of the MN1 gene at chromosomal location 22q12.1 and the BEND2 gene at Xp22.13. Other emerging pediatric CNS tumor entities demonstrating ependymal or astroblastoma-like histological features also harbor gene fusions involving chromosome X, 11q22 and 22q12 breakpoint regions.

CONCLUSIONS

Genomic DNA profiling has facilitated discovery of several new CNS tumor entities, however, traditional methods, such as immunohistochemistry, DNA or RNA sequencing, and cytogenetic studies, including fluorescence in situ hybridization, remain necessary for their accurate biological classification and diagnosis.

The spectrum of morphological findings in pediatric central nervous system MN1-fusion-positive neuroepithelial tumors

PURPOSE

Central nervous system high-grade neuroepithelial tumor with MN1 alteration (CNS-HGNET-MN1) is a rare entity defined by its DNA methylation pattern and pathologically considered to be high-grade with mixed patterns, stromal hyalinization, and with astrocytic differentiation. Our aim was to present six pediatric cases to contribute to the characterization of this group of tumors.

MATERIAL AND METHODS

Six female patients aged 4 to 12 years with CNS tumors with MN1 alteration identified using genome-wide methylation arrays and/or RT-PCR were included. Clinicopathological, morphological, immunohistochemical, and molecular findings were analyzed.

RESULTS

Tumor location was the parietal lobe in four and the intramedullary spinal cord in two. Two were morphologically diagnosed as ependymomas, one as gliofibroma, one as a HGNET-MN1 altered and the other two were difficult to classify. All were well-defined tumors, with a cystic component in three. Only two tumors had extensive stromal hyalinization, three had pseudopapillary formations, and four had other patterns. Multinucleated, clear, and rhabdoid cells were present. Necrosis and histiocyte clusters were also observed. Proliferative index was >10 in four. GFAP, EMA, CK, and SYN were variable, while Olig2 staining was mostly positive. Four of six patients with supratentorial tumors and complete resections were alive and tumor free after 2 to 10 years of follow-up. The two cases with medullary involvement and incomplete resections were alive and undergoing treatment 2 years after surgery.

CONCLUSION

Neuroepithelial-MN1 tumors are challenging and suspicion requires molecular confirmation. Our pediatric data contribute to the knowledge for accurate diagnosis. Although further studies with a larger number of cases should be conducted in order to draw more robust conclusions regarding clinico-pathological features, here we present valuable pediatric data to increase the knowledge that may lead to the accurate management of this group of tumors.

MN1 altered astroblastoma with APC and LRP1B gene mutations: a unique variant in the cervical spine of a pediatric patient

PURPOSE

Astroblastomas (AB) are high-grade neoplasms which typically occur within the cerebral hemisphere. However, given the rarity of this neoplasm and the number of variants, the relevance of this molecular makeup is unknown. We sought to describe the clinical presentation, treatment, and pathological analysis of a novel MN1 (meningioma 1) cervical spinal cord astroblastoma variant presenting in a pediatric patient.

METHODS

A retrospective review of electronic medical records was performed with an emphasis on neuroimaging, perioperative course, and pathological analysis.

RESULTS

An 11-month-old male with no significant history presented with two weeks of neck stiffness and cervicalgia. Neurologically, the patient was intact without signs of infection or trauma. Cervical CT was unremarkable. A subsequent MRI demonstrated a heterogeneously enhancing intramedullary lesion extending from the craniocervical junction to T4. The patient was treated with perioperative steroids and underwent C1-C3 laminectomies and C4-T4 laminotomies for tumor resection. Upon completion of the durotomy, an exophytic gray-red tumor was appreciated within the epidural space and gross total resection was achieved (no change on intraoperative neurophysiological monitoring) and confirmed on post-operative imaging. Immunohistochemical analysis was consistent with an astroblastoma with atypical diffuse positivity of CD56, CD99, and nuclear OLIG2. Molecular analysis revealed not only MN1 alterations but also changes in genes encoding APC and LRP1B. Both alterations were not previously documented to be associated with an astroblastoma.

CONCLUSION

Our case represents the first report of an infant with an MN1 astroblastoma with APC and LRP1B gene alterations in the cervical spine. Gross total resection paired with a detailed histopathologic analysis is vital for optimizing adjuvant treatment.

Recurrent HGNET-MN1 altered (astroblastoma MN1-altered) of the foramen magnum: Case report and molecular classification

Background

Astroblastoma is a rare primary brain tumor of unclear origin, often occurring in young patients less than 30-years-old. It typically arises supratentorially and is diagnosed based on histological features including vascular hyalinization and perivascular pseudorosettes. Recent molecular characterization of primary CNS high-grade neuroepithelial tumors with meningioma I alteration (HGNET-MN1) found that HGNET-MN1 and tumors with morphological signatures of astroblastoma clustered together. Further analysis revealed such astroblastomas have MN1 alteration and the 2021 WHO classification of tumors of the CNS now recognizes astroblastoma MN1-altered as a new entity.

Case Description

Here, we present the case of a 36-year-old right-handed woman with recurrent low-grade astroblastoma in the cervicomedullary junction. The patient presented with worsening motor and sensory deficits of her upper extremities, pain, ataxia, visual disturbance, and nausea. Due to extensive recurrence and neurological symptoms, the patient underwent reoperation.

Conclusion

We review a rare case of recurrent astroblastoma in the foramen magnum in light of new relevant literature about tumor biology and prognostic significance of the new classification of astroblastoma MN1-altered.

Clinicoradiological and histopathological characteristics and treatment outcomes of cerebral astroblastoma in children: a single-institution experience

OBJECTIVE

Astroblastoma (AB) is a rare glial tumor. The optimal treatment and prognosis of this tumor remain unclear. The authors retrospectively analyzed the clinical characteristics, neuroimaging findings, histopathological results, and treatment outcomes of 7 patients with AB.

METHODS

The study comprised 7 patients with pathologically proven AB who were surgically treated at Samsung Medical Center from November 1994 to January 2019. Clinicoradiological, histopathological, and surgical records were reviewed.

RESULTS

The patients included 5 girls (71.4%) and 2 boys (28.6%), with a median age of 13 years. All patients showed contrast enhancement on preoperative MRI: 5 ABs (71.4%) showed a concomitant solid and cystic appearance, and 2 (28.6%) demonstrated a solid appearance. ABs in 6 patients (85.7%) showed a well-circumscribed, characteristic "bubbly" appearance on T2-weighted MRI. Gross-total resection (GTR) was achieved in all cases (100%). Six patients (85.7%) were diagnosed with high-grade AB and 1 (14.3%) with low-grade AB. Six (85.7%) of the 7 patients received adjuvant treatment after resection, including 5 (83.3%) with AB who received chemotherapy and radiotherapy and 1 (16.7%) who received proton therapy alone. The median clinical follow-up duration was 96 months (range 48-189 months). Two patients experienced recurrence, and all patients in this series were alive at the last follow-up.

CONCLUSIONS

In this study, the clinicoradiological and histopathological features of AB were described. Based on the authors' limited experience with 7 cases, resection with the goal of GTR is currently the mainstream treatment for AB, and adjuvant radiation treatment should be considered after surgery.

Neuroimaging of astroblastomas: A case series and systematic review

BACKGROUND AND PURPOSE

Astroblastoma is a rare type of glial tumor, histologically classified into two types with different prognoses: high and low grade. We aimed to investigate the CT and MRI findings of astroblastomas by collecting studies with analyzable neuroimaging data and extracting the imaging features useful for tumor grading.

METHODS

We searched for reports of pathologically proven astroblastomas with analyzable neuroimaging data using PubMed, Scopus, and Embase. Sixty-five studies with 71 patients with astroblastomas met the criteria for a systematic review. We added eight patients from our hospital, resulting in a final study cohort of 79 patients. The proportion of high-grade tumors was compared in groups based on the morphology (typical and atypical) using Fisher's exact test.

RESULTS

High- and low-grade tumors were 35/71 (49.3%) and 36/71 (50.7%), respectively. There was a significant difference in the proportion of high-grade tumors based on the tumor morphology (typical morphology: high-grade = 33/58 [56.9%] vs. atypical morphology, 2/13 [15.4%], p = .012). The reviews of neuroimaging findings were performed using the images included in each article. The articles had missing data due to the heterogeneity of the collected studies.

CONCLUSIONS

Detailed neuroimaging features were clarified, including tumor location, margin status, morphology, CT attenuation, MRI signal intensity, and contrast enhancement pattern. The classification of tumor morphology may help predict the tumor's histological grade, contributing to clinical care and future oncologic research.

A pediatric cerebral tumor with MN1 alteration and pathological features mimicking carcinoma metastasis: may the terminology "high grade neuroepithelial tumor with MN1 alteration" still be relevant?

INTRODUCTION

Astroblastoma, MN1-altered (old name: high-grade neuroepithelial tumor/HGNET with MN1 alteration) is a recently described central nervous system tumor mostly affecting pediatric patients and profoundly young girls. Differential pathological diagnoses of these tumors include ependymoma, pleomorphic xanthoastrocytoma, embryonal tumor with multilayered rosettes, meningioma, and even glioblastoma. As the treatment approaches to these tumors differ, it is essential to increase the awareness about these tumors in the neurosurgical community.

CLINICAL PRESENTATION

A 7-year-old female patient admitted with a 7-day history of headache, nausea, and vomiting. A contrasted MRI scan revealed a left parietal 4 × 4 × 5 cm mass with central necrosis and peripheral contrast enhancement. The tumor's histopathological findings were suggestive of a metastatic carcinoma with unknown primary, yet further genetic analysis revealed MN1 alteration. Peculiarly, the tumor pathomorphological features were not compatible with astroblastomas and exerted features strongly indicating a metastatic cancer; however, systemic PET and whole-body MRI failed to detect a primary malignancy.

OUTCOME AND CONCLUSIONS

Eighteen months after gross-total tumor resection, an in-field and out-field multifocal recurrence developed which required a second surgery and subsequent chemo-radiotherapy. The patient is doing well for 1 year after the second treatment regimen at the time of this report. Despite the final cIMPACT6 classification in 2020 advised to define all MN1 altered brain tumors as astroblastomas, there exist prognostic differences in MN1-altered tumors with and without morphological features of astroblastoma. Rare morphological variants of MN1-altered tumors shall be recognized for their future prognostic and clinical classification. HGNET with MN1 alteration seems still be a more proper definition of such malignancies as an umbrella term.

Spinal cord astroblastoma with EWSR1-BEND2 fusion classified as HGNET-MN1 by methylation classification: a case report

The most recurrent fusion of central nervous system high-grade neuroepithelial tumor with MN1 alteration (HGNET-MN1) is MN1 rearrangement. Here, we report the case of a 36-year-old man with spinal cord astroblastoma showing Ewing Sarcoma breakpoint region 1/EWS RNA-binding protein 1 (EWSR1)-BEN domain-containing 2 (BEND2) fusion. The patient presented with back pain, gait disturbance and dysesthesia in the lower extremities and trunk. Magnetic resonance imaging showed an intramedullary tumor at the T3-5 level, displaying homogeneous gadolinium enhancement. Partial tumor removal was performed with laminectomy. Histological examinations demonstrated solid growth of epithelioid tumor cells showing high cellularity, a pseudopapillary structure, intervening hyalinized fibrous stroma, and some mitoses. Astroblastoma was diagnosed, classified as HGNET-MN1 by the German Cancer Research Center methylation classifier. MN1 alteration was not detected by fluorescence in situ hybridization (FISH), but EWSR1-BEND2 fusion was detected by FISH and RNA sequencing. Previously, a child with EWSR1-BEND2 fusion-positive spinal astroblastoma classified as HGNET-MN1 was reported. In conjunction with that, the present case provides evidence that EWSR1-BEND2 fusion is identified in the entity of HGNET-MN1. Taken together, the BEND2 alteration rather than MN1 may determine the biology of a subset of the central nervous system HGNET-MN1 subclass.

Treatment response of CNS high-grade neuroepithelial tumors with MN1 alteration

Central nervous system high-grade neuroepithelial tumor with MN1 alteration (CNS HGNET-MN1) is a rare recently described entity. Fourteen CNS HGNET-MN1 patients were identified using genome-wide methylation arrays/RT-PCR across seven institutions. All patients had surgery (gross total resection: 10; subtotal resection: four) as initial management followed by observation alone in three patients, followed by radiotherapy in eight patients (focal: five; craniospinal: two; CyberKnife: one) and systemic chemotherapy in three patients. Seven patients relapsed; five local and two metastatic, despite adjuvant radiotherapy, of which three died. Treatment of CNS HGNET-MN1 remains a major treatment challenge despite aggressive surgical resections and upfront radiotherapy, warranting new approaches to this rare malignancy.

Well-differentiated Astroblastoma with Both Focal Anaplastic Features and a Meningioma 1 Gene Alteration

A 6-year-old female was incidentally found to have a brain tumor. Magnetic resonance imaging (MRI) demonstrated a gadolinium-enhanced mass in the left parietal lobe. We performed gross total resection with the assistance of fluorescent guidance by 5-aminolevulinic acid (5-ALA). A histological examination of the tumor specimen showed well-differentiated astroblastic features with focal anaplasia. Fluorescence in situ hybridization (FISH) revealed meningioma 1 (MN1) gene alteration and supported our diagnosis. She received local radiotherapy and oral temozolomide followed by maintenance temozolomide chemotherapy, and the tumor was well controlled without any neurological deficit for 27 months. Our case is considered to be valuable since it describes a patient who is diagnosed to have a well-differentiated astroblastoma with both focal anaplastic features and MN1 gene rearrangement. A larger study is warranted to establish evidence supporting the diagnosis and treatment of astroblastoma with molecular characteristic features. MN1 alteration will be a diagnostic marker for astroblastoma in the future.

Central nervous system neuroepithelial tumors with MN1-alteration: an individual patient data meta-analysis of 73 cases

MN1 alteration characterizes a recently described group of neuroepithelial tumors with varied morphological features. In cIMPACT-NOW update 6, only those with astroblastoma morphology has been accepted as a newly recognized tumor type, whereas the rest of morphological variants are considered lesions sub-judice. We perform an individual patient data meta-analysis of MN1-altered neuroepithelial tumors comprising a total of 73 cases, in order to study the survival data and predictive markers for better diagnosis and management of this rare molecular entity. The 5- and 10-year progression-free survival are 38% and 0%, whereas the 5- and 10-year overall survival are 89% and 55%, respectively. Among all the morphological variants of MN1-altered tumor, astroblastoma morphology is significantly associated with an improved overall survival, emphasizing the importance of providing an integrated histologic and molecular diagnosis. Histological grading within the molecularly-defined MN1-altered astroblastoma remains controversial. In tumors with astroblastoma morphology, the odds of MN1-altered status among patients less than 15-year-old is 10.5 times that of those 15-year-old and older, and female of 9.4 times that of the male gender. Gross tumor resection appears as main treatment modality for better disease control based on observational data.

Posterior fossa astroblastoma in a child: a case report and a review of the literature

A 4-year-old girl presented to the hospital with a progressive headache, difficulty walking, and persistent daily vomiting for 3 weeks. Papilledema was observed on fundoscopic examination. A large left cerebellovermian tumor with "bubbly" appearance was discovered. Total removal of the tumor mass was performed, and a diagnosis of low-grade astroblastoma was made. Adjuvant radiotherapy was performed due to the risk of recurrence. The patient is disease-free and has been kept on close follow-up for 6 months. The occurrence of posterior fossa astroblastoma has been rarely reported in the literature. Thus, when a "bubby" appearance enhancing cystic solid tumor is located on the cerebellar hemisphere in a child, an astroblastoma should also be included in the differential diagnosis.

Role of DNA Methylation Profile in Diagnosing Astroblastoma: A Case Report and Literature Review

Astroblastoma is a rare tumor of the central nervous system (CNS) with uncertain clinical behavior. Recently, DNA methylation profiling has been shown to provide a highly robust and reproducible approach for the classification of all CNS tumors across different age groups. By using DNA methylation profiling, a subset of CNS high-grade tumors with astroblastoma-like morphology characterized by the meningioma 1 gene (MN1) rearrangements, has been identified; they were termed “CNS high-grade neuroepithelial tumors with MN1 alteration” (CNS-HGNET-MN1). Here, we describe a case of CNS-HGNET-MN1 diagnosed by DNA methylation profiling, using Illumina Infinium HumanMethylationEPIC BeadChip (EPIC), that offers the opportunity to conduct a brief literature review. The patient presented with an episode of partial seizures involving the right hemisoma. A gross total resection was performed. No other treatment was proposed in light of the histological and molecular findings. After 21 months, the patient is disease-free in good clinical conditions. Also in view of this case, we recommend DNA-methylation profiling as an important tool for diagnosis and more effective patient stratification and management.