Spinal cord astroblastoma with an EWSR1-BEND2 fusion classified as a high-grade neuroepithelial tumour with MN1 alteration

Spinal Cord Astroblastoma With EWSR1-BEND2 Fusion in Female Patients: A Report of Four Cases From China and a Comprehensive Literature Review

Astroblastoma is an extremely rare central nervous system tumor characterized by astroblastic pseudorosettes and vascular hyalinization. Despite these histologic hallmarks, its morphology can vary, occasionally resembling other central nervous system tumors such as ependymoma. A novel tumor entity, astroblastoma, meningioma 1 (MN1)-altered, has been identified, featuring MN1 gene rearrangements typically involving BEN-domain containing 2 (BEND2) as a fusion partner. Most astroblastomas arise in the cerebral hemisphere. Here, we report 4 cases of spinal cord astroblastoma in female patients, all showing Ewing sarcoma RNA-binding protein 1 fusion with BEND2, rather than MN1. These tumors displayed growth patterns akin to traditional intracranial astroblastomas, with three cases demonstrating high-grade histology, including elevated mitotic activity and necrosis. Interestingly, some cases exhibited positive staining for pan-cytokeratin and hormone receptors. DNA methylation profiling clustered three of the four cases with the reference "AB_EWSR," whereas one case exhibited an independent methylation signature near the reference methylation group "AB_EWSR" and "pleomorphic xanthoastrocytoma." Together with the existing literature, we summarized a total of eleven cases, which predominantly affected children and young adults with female predilection. Eight of 10 patients experienced recurrence, underscoring the aggressive nature of this disease. We suggest recognizing a new molecular subgroup of spinal astroblastoma and recommend testing newly diagnosed infratentorial astroblastomas for Ewing sarcoma RNA-binding protein 1-BEND2 fusion.

Spinal astroblastoma, MN1 altered in 3-year-old child: An uncommon tumor at an unusual site

Astroblastoma is an uncommon circumscribed glial tumor mostly involving the cerebral hemisphere. The characteristic molecular alteration is meningioma (disrupted in balanced translocation) 1 (MN1) rearrangement. No definite World Health Organization grade has been assigned as both low- and high-grade tumors are known to occur. Tumors in the spine are extremely rare; to date only three cases have been reported in the literature. A vigilant microscopy and ancillary testing aid in diagnosis when the tumors present in unusual locations, as in our case. The prompt differentiation of this tumor from its mimickers is a mandate as modalities of management are different and not clearly established.

An Exome Capture-Based RNA-Sequencing Assay for Genome-Wide Identification and Prioritization of Clinically Important Fusions in Pediatric Tumors

This study reports the development of an exome capture-based RNA-sequencing assay to detect recurring and novel fusions in hematologic, solid, and central nervous system tumors. The assay used Twist Comprehensive Exome capture with either fresh or formalin-fixed samples and a bioinformatic platform that provides fusion detection, prioritization, and downstream curation. A minimum of 50 million uniquely mapped reads, a consensus read alignment/fusion calling approach using four callers (Arriba, FusionCatcher, STAR-Fusion, and Dragen), and custom software were used to integrate, annotate, and rank the candidate fusion calls. In an evaluation of 50 samples, the number of calls varied substantially by caller, from a mean of 24.8 with STAR-Fusion to 259.6 with FusionCatcher; only 1.1% of calls were made by all four callers. Therefore a filtering and ranking algorithm was developed based on multiple criteria, including number of supporting reads, calling consensus, genes involved, and cross-reference against databases of known cancer-associated or likely false-positive fusions. This approach was highly effective in pinpointing known clinically relevant fusions, ranking them first in 47 of 50 samples (94%). Detection of pathogenic gene fusions in three diagnostically challenging cases highlights the importance of a genome-wide and nontargeted method for fusion detection in pediatric cancer.

Identification of Novel/Rare EWSR1 Fusion Partners in Undifferentiated Mesenchymal Neoplasms

Recurrent gene fusions (GFs) in translocated sarcomas are recognized as major oncogenic drivers of the disease, as well as diagnostic markers whose identification is necessary for differential diagnosis. EWSR1 is a 'promiscuous' gene that can fuse with many different partner genes, defining different entities among a broad range of mesenchymal neoplasms. Molecular testing of EWSR1 translocation traditionally relies on FISH assays with break-apart probes, which are unable to identify the fusion partner. Therefore, other ancillary molecular diagnostic modalities are being increasingly adopted for accurate classification of these neoplasms. Herein, we report three cases with rare GFs involving EWSR1 in undifferentiated mesenchymal neoplasms with uncertain differential diagnoses, using targeted RNA-seq and confirming with RT-PCR and Sanger sequencing. Two GFs involved hormone nuclear receptors as 3' partners, NR4A2 and RORB, which have not been previously reported. NR4A2 may functionally replace NR4A3, the usual 3' partner in extraskeletal myxoid chondrosarcoma. The third GF, EWSR1::BEND2, has previously been reported in a subtype of astroblastoma and other rare entities, including a single case of a soft-tissue tumor that we discuss in this work. In conclusion, our findings indicate that the catalogue of mesenchymal neoplasm-bearing EWSR1 fusions continues to grow, underscoring the value of using molecular ancillary techniques with higher diagnostic abilities in the routine clinical setting.

[Contributions and limitations of FISH analysis for the diagnosis of central nervous system tumors according to the 2021 WHO classification: Feedback from Sainte-Anne Hospital's Department of Neuropathology]

The fifth edition of the World Health Organization (WHO) Classification of Tumors of the Central Nervous System has identified many new tumor types and has established, for the first time, essential and desirable diagnostic criteria for each of them. Among these, genetic alterations play an important role associated with morphology. For the first time, epigenetic data can also constitute essential and/or desirable criteria. These genetic abnormalities can be fusions, deletions or gains/amplifications and can thus be detected by fluorescence in situ hybridization techniques. The purpose of this article is to present the advantages and limitations of this technique in reference to its specific use within neuro-oncopathology in light of the 2021 WHO classification.

A Low-grade Sinonasal Sarcoma Harboring EWSR1::BEND2: Expanding the Differential Diagnosis of Sinonasal Spindle Cell Neoplasms

BACKGROUND

Molecular diagnostics has greatly refined sinonasal tumor pathology over the past decade. While much of the attention has focused on carcinomas, it is becoming clear that there are emerging mesenchymal neoplasms which have previously defied classification.

METHODS

Here, we present a 33-year-old woman with a multiply recurrent sinonasal spindle cell tumor exhibiting distinctive features, and not easily classifiable into a specific category.

RESULTS

The hypercellular tumor was composed of plump spindled cells, with uniform vesicular chromatin arranged as vague fascicles around a prominent hemangiopericytoma-like vasculature. The mitotic rate was brisk at 10 per 10 high power fields. By immunohistochemistry, it was only positive for EMA (focal) and SATB2 (diffuse, weak). Fusion analysis uncovered EWSR1::BEND2, a fusion which is best known for being seen in astroblastoma, but which has not yet been reported in sarcomas.

CONCLUSION

This case underscores the utility of fusion analysis when confronted with a sinonasal spindle cell neoplasm which does not neatly fit into any specific category. It remains to be seen if EWSR1::BEND2 sinonasal sarcoma represents a distinct entity.

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.

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.

Case report: Novel NIPBL-BEND2 fusion gene identified in osteoblastoma-like phosphaturic mesenchymal tumor of the fibula

Phosphaturic mesenchymal tumor (PMT) is a rare tumor that secretes fibroblast growth factor 23 (FGF23) and causes hypophosphatemia and tumor-induced osteomalacia (TIO). Fusion genes FN1-FGFR1 and FN1-FGF1 have been detected in some PMTs, but the pathogenesis of PMTs without these fusion genes remains unclear. Here, we report a 12-year-old boy with persistent muscle weakness and gait disturbance. Roentgenographic examination revealed a radiolucent lesion with endosteal scalloping in the left fibula, while his serum level of FGF23 was markedly increased. Combined with simple X-ray findings of other body parts, we suspected that TIO was caused by PMT, and resected the tumor. After resection, the serum level of FGF23 started to decrease immediately and normalized within 3 hours after resection, with this being earlier than normalization of the serum phosphorus level. In RNA sequencing, FN1-FGFR1 and FN1-FGF1 were not detected, but a novel NIPBL-BEND2 fusion gene was identified. When we forcedly expressed this fusion gene in HEK293T cells and MG63 cells, cell proliferation was enhanced in both cell lines. Furthermore, Gene set enrichment analysis of HEK293T cells showed significant upregulation of MYC-target genes. Our results suggest that this novel NIPBL-BEND2 fusion gene promotes cell proliferation possibly via the MYC pathway and might be one of the etiologies of PMTs other than FN1-FGFR1 or FN1-FGF1.

Spinal astroblastoma: a rare tumour in an unusual location

Astroblastomas are central nervous system tumours with unknown cell of origin and clinical behaviour. These tumours occur most commonly in cerebral hemispheres with spinal astroblastomas being very rare. We report a case of spinal astroblastoma which harboured MN1 alteration.

Soft-tissue sarcoma with MN1-BEND2 fusion: A case report and comparison with astroblastoma

MN1-BEND2 is considered as a defining gene fusion of astroblastoma. Herein, we report the first case of soft-tissue sarcoma with this fusion. The tumor developed in the abdominal wall of an 87-year-old woman, and consisted of a striking storiform growth of low-grade spindle cells admixed with a dense proliferation of oval cells with a higher nuclear atypia and mitotic activity. The sarcoma was immunohistochemically positive for actin but negative for S100 protein, glial fibrillary acidic protein, and Olig2. Targeted RNA sequencing identified an in-frame MN1 (exon 1)-BEND2 (exon 11) fusion transcript, which was validated by reverse transcription polymerase chain reaction, Sanger sequencing, and MN1 break-apart fluorescence in situ hybridization. DNA methylation profiling revealed that the tumor did not match any sarcoma classes based on the DKFZ classifier. Using T-distributed stochastic neighbor embedding analysis, the sarcoma was plotted close to the provisional class "Sarcoma (malignant peripheral nerve sheath tumor-like)," despite no phenotypic resemblance. Copy number analysis using methylation data demonstrated losses at 2q, 8p, 9p, 11p, 14q, 19q, and 22q. When compared with a cerebral astroblastoma sample with MN1 (exon 1)-BEND2 (exon 9) fusion, the sarcoma showed no resemblance in histology, immunophenotype, or DNA methylation profile, although they shared copy number loss at 14q, 19q, and 22q. The present report demonstrated that MN1-BEND2 is another example of a pleiotropic fusion gene that is shared among different tumor types.

Identification and characterization of BEND2 as a key regulator of meiosis during mouse spermatogenesis

The chromatin state, which undergoes global changes during spermatogenesis, is critical to meiotic initiation and progression. However, the key regulators involved and the underlying molecular mechanisms remain to be uncovered. Here, we report that mouse BEND2 is specifically expressed in spermatogenic cells around meiotic initiation and that it plays an essential role in meiotic progression. Bend2 gene knockout in male mice arrested meiosis at the transition from zygonema to pachynema, disrupted synapsis and DNA double-strand break repair, and induced nonhomologous chromosomal pairing. BEND2 interacted with chromatin-associated proteins that are components of certain transcription-repressor complexes. BEND2-binding sites were identified in diverse chromatin states and enriched in simple sequence repeats. BEND2 inhibited the expression of genes involved in meiotic initiation and regulated chromatin accessibility and the modification of H3K4me3. Therefore, our study identified BEND2 as a previously unknown key regulator of meiosis, gene expression, and chromatin state during mouse spermatogenesis.

Astroblastomas exhibit radial glia stem cell lineages and differential expression of imprinted and X-inactivation escape genes

Astroblastomas (ABs) are rare brain tumors of unknown origin. We performed an integrative genetic and epigenetic analysis of AB-like tumors. Here, we show that tumors traceable to neural stem/progenitor cells (radial glia) that emerge during early to later brain development occur in children and young adults, respectively. Tumors with MN1-BEND2 fusion appear to present exclusively in females and exhibit overexpression of genes expressed prior to 25 post-conception weeks (pcw), including genes enriched in early ventricular zone radial glia and ependymal tumors. Other, histologically classic ABs overexpress or harbor mutations of mitogen-activated protein kinase pathway genes, outer and truncated radial glia genes, and genes expressed after 25 pcw, including neuronal and astrocyte markers. Findings support that AB-like tumors arise in the context of epigenetic and genetic changes in neural progenitors. Selective gene fusion, variable imprinting and/or chromosome X-inactivation escape resulting in biallelic overexpression may contribute to female predominance of AB molecular subtypes.

High-grade glioma with pleomorphic and pseudopapillary features (HPAP): a proposed type of circumscribed glioma in adults harboring frequent TP53 mutations and recurrent monosomy 13

Tumors of the central nervous system (CNS) often display a wide morphologic spectrum that has, until recently, been the sole basis for tumor classification. The introduction of the integrated histomolecular diagnostic approach in CNS tumors has facilitated a classification system that is increasingly data-driven and with improved alignment to clinical outcome. Here, we report a previously uncharacterized glioma type (n = 31) using unsupervised clustering analysis of DNA methylation array data from approximately 14,000 CNS tumor samples. Histologic examination revealed circumscribed growth and morphologic similarities to pleomorphic xanthoastrocytoma (PXA), astroblastoma, ependymoma, polymorphous neuroepithelial tumor of the young (PLNTY), and IDH-wildtype glioblastoma (GBM). Median age (46.5 years) was significantly older than other circumscribed gliomas and younger than GBM. Dimensionality reduction with uniform manifold approximation and projection (UMAP) and hierarchical clustering confirmed a methylation signature distinct from known tumor types and methylation classes. DNA sequencing revealed recurrent mutations in TP53 (57%), RB1 (26%), NF1 (26%), and NF2 (14%). BRAF V600E mutations were detected in 3/27 sequenced cases (12%). Copy number analysis showed increased whole chromosome aneuploidy with recurrent loss of chromosome 13 (28/31 cases, 90%). CDKN2A/B deletion (2/31, 6%) and MGMT promoter methylation (1/31, 3%) were notably rare events. Most tumors showed features of a high-grade glioma, yet survival data showed significantly better overall survival compared to GBM (p < 0.0001). In summary, we describe a previously uncharacterized glioma of adults identified by a distinct DNA methylation signature and recurrent loss of chromosome 13.

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.

Identification of novel SSX1 fusions in synovial sarcoma

Synovial sarcoma is characterized by variable epithelial differentiation and specific SS18-SSX gene fusions. The diagnosis is primarily based on phenotype, but fusion gene detection is increasingly being considered indispensable, with SS18 break-apart fluorescence in situ hybridization (FISH) being favored in many laboratories. However, SS18 FISH assay produces negative or atypical results in a minority of cases, leaving uncertainties in diagnosis and management. Here, we analyzed this challenging subset of SS18 FISH-negative/atypical synovial sarcoma using RNA sequencing and monoclonal antibodies that recognize SS18-SSX and the SSX C-terminus. Among 99 synovial sarcoma cases that were previously subjected to SS18 break-apart FISH, eight cases were reported as negative and three cases were indeterminate, owing to atypical signal patterns. Three of these 11 tumors (two monophasic and one biphasic) harbored novel EWSR1-SSX1 fusions, were negative for SS18-SSX staining, and were positive for SSX C-terminus staining. One monophasic tumor harbored a novel MN1-SSX1 fusion, and showed negative SS18-SSX expression and positive SSX C-terminus staining. Another monophasic tumor carried an SS18L1-SSX1 fusion, and was weakly positive for SS18-SSX, while SMARCB1 expression was reduced. The presence of these novel and/or rare fusions was confirmed using RT-PCR and Sanger sequencing. EWSR1-SSX1 was further validated by EWSR1 FISH assay. The remaining six tumors (five monophasic and one biphasic) showed strong SS18-SSX expression, and RNA sequencing successfully performed in three cases identified canonical SS18-SSX2 fusions. Based on a DNA methylation-based unsupervised clustering, the tumors with EWSR1-SSX1 and SS18L1-SSX1 clustered with synovial sarcoma, while the MN1-SSX1-positive tumor was not co-clustered despite classic histology and immunoprofile. In summary, we discovered novel and rare SSX1 fusions to non-SS18 genes in synovial sarcoma. The expanded genetic landscape carries significant diagnostic implications and advances our understanding of the oncogenic mechanism.

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.

Molecular profiling of pediatric and adolescent ependymomas: identification of genetic variants using a next-generation sequencing panel

PURPOSE

Ependymoma (EPN) accounts for approximately 10% of all primary central nervous system (CNS) tumors in children and in most cases, chemotherapy is ineffective and treatment remains challenging. We investigated molecular alterations, with a potential prognostic marker and therapeutic target in EPNs of childhood and adolescence, using a next-generation sequencing (NGS) panel specific for pediatric neoplasms.

METHODS

We selected 61 samples with initial diagnosis of EPN from patients treated at Pediatric Oncology Institute-GRAACC/UNIFESP. All samples were divided according to the anatomical compartment of the CNS - 42 posterior fossa (PF), 14 supratentorial (ST), and five spinal (SP). NGS was performed to identify somatic genetic variants in tumor samples using the Oncomine Childhood Cancer Research Assay® (OCCRA®) panel, from Thermo Fisher Scientific®.

RESULTS

Genetic variants were identified in 24 of 61 (39.3%) tumors and over 90% of all variants were pathogenic or likely pathogenic. The most commonly variants detected were in CIC, ASXL1, and JAK2 genes and have not been reported in EPN yet. MN1-BEND2 fusion, alteration recently described in a new CNS tumor type, was identified in one ST sample that was reclassified as astroblastoma. Additionally, YAP1-MAMLD1 fusion, a rare event associated with good outcome in ST-EPN, was observed in two patients diagnosed under 2 years old.

CONCLUSIONS

Molecular profiling by the OCCRA® panel showed novel alterations in pediatric and adolescent EPNs, which highlights the clinical importance in identifying genetic variants for patients' prognosis and therapeutic orientation.

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.

Rhabdoid tumor predisposition syndrome with renal tumor 10 years after brain tumor

We report a case of rhabdoid tumor predisposition syndrome with a renal tumor developing 10 years after a brain tumor, which demonstrated an unexpectedly favorable outcome. A 2-year-old boy underwent gross total resection of a brain tumor located in the fourth ventricle, and received adjuvant chemotherapy and radiotherapy. At the age of 11 years, a renal tumor was found and nephrectomy was performed. He is currently alive without evidence of disease over 2 years without postoperative therapy. Histologically, rhabdoid cells were observed in both brain and renal tumors. Loss of SMARCB1 (also known as INI1) expression was found in the nucleus of both tumor cells. Genetic testing revealed pathogenic variants of SMARCB1 exon 5 in the renal tumor and SMARCB1 exon 9 in the brain tumor. In addition, heterozygous deletion of 22q11.21-q11.23 containing the SMARCB1 locus was shared by both tumors and this deletion was identified in normal peripheral blood. Considering the histopathological and genetic findings, our case was considered to be rhabdoid tumor predisposition syndrome with atypical teratoid/rhabdoid tumor and late-onset rhabdoid tumor of the kidney.

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.