Long-Term Follow-Up of a Child with EWSR1-BEND2 Fused Spinal Astroblastoma

Astroblastoma is a rare high-grade neuroepithelial tumor usually occurring in children and young adults with a clear female predominance, typically located in the cerebral hemispheres [1‒7]. Very few cases of spinal astroblastoma have been described in the literature so far. Astroblastoma was first described as a distinct tumor entity by Bailey and Cushing in 1926 [8‒11]. These tumors have diverse morphological features with overlapping astrocytic and ependymal characteristics. The typical histopathological appearance is the astroblastomatous rosette, which is also seen in other central nervous system (CNS) tumors [12], including BRAF-mutant pleomorphic xanthoastrocytoma, ZFTA-fused supratentorial ependymoma, and IDH wild-type glioblastoma [13]. Recent advances in molecular diagnostics have allowed further differentiation of astroblastoma from other tumors. Seventy percent of tumors histologically classified as astroblastoma have a structural rearrangement in the MN1 proto-oncogene on chromosome 22. MN1-altered astroblastomas were described in 2016 by Sturm et al. [14] as a distinct epigenetic tumor cluster, characterized as high-grade neuroepithelial tumors of the CNS with MN1-alteration (HGNET-MN1). Although the identification of an MN1-alteration classifies astroblastoma as a type of circumscribed astrocytic glioma in the WHO 2021 CNS Tumor Classification, it is not required for diagnosis. MN1-altered astroblastoma probably represents a variant of astroblastoma.

Investigation of the molecular signature of these tumors is critical for the development of targeted therapies. EWSR1-BEND2 fusion was first described by Tsutsui et al. in 2021. Since then, several cases of spinal astroblastoma with the same fusion have been published. The EWSR1 gene is ubiquitously expressed in most cell types and plays an epigenetic role in gene expression, RNA processing, and cellular signaling [15]. In several malignancies, the N-terminal activation domain of EWSR1 has been shown to fuse with the DNA-binding domain of several transcription factors, leading to the generation of oncogenic transcription factors [16]. The direct role of the EWSR1-BEND2 fusion in tumorigenesis remains to be determined [17]. EWSR1 fusion appears to be more common in brainstem and spinal cord astroblastomas compared to MN1 fusion in hemispheric astroblastomas, which previously led to the speculation that these represent two distinct subtypes of astroblastoma [13]. Due to the rarity of this tumor, a differentiated therapeutic strategy has not yet been established.

A 3-year-old girl was diagnosed with a C2-C7 intramedullary tumor in the clinical context of limping in her right leg. Partial resection of the tumor was performed (Fig. 1a), resulting in complete postoperative paraplegia and weakness of both upper extremities. The histopathologic diagnosis was compatible with an anaplastic ependymoma. Subsequently, the patient underwent two cycles of chemotherapy (HIT-SKK chemotherapy) [18, 19] followed by spinal radiotherapy with a total dose of 44.2 Gy. Twelve months after surgery, follow-up (FU) MRI revealed tumor progression (Fig. 1b). A chemotherapy regimen of 6 cycles of Vincristine-Irinotecan-Temodal was discontinued after four cycles due to severe intolerance. Subsequent MRI scans showed no further tumor progression.

Sixty-three months after the primary surgery, at the age of 8, an MRI showed new progression of the disease (Fig. 1c). At this point, the family moved from their home country to Switzerland, where they were referred to another institution within the country. At this stage, the patient had severe tetraparesis with partial distal movement in the upper limbs and limited bladder control (mostly diurnal). After discussion with the family and in order to preserve her functions as well as to confirm diagnosis, an open biopsy was performed 3 months after the radiological diagnosis of recurrence. The patient’s neurological status remained unchanged after surgery. An Individualized Molecular Tumor Analysis (INFORM) revealed an EWSR1-BEND2 fusion, consistent with the diagnosis of astroblastoma. Two months later, a new progression of the tumor was observed on MRI. An ambulatory treatment strategy appeared in this heavily pretreated patient most appropriate, thus a treatment according to MEMMAT protocol [20] was initiated. A ventricular drain with Omaya reservoir and a port-a-cath were implanted. Over the course of treatment, the patient remained stable over many months before showing progressive impairment of hand dexterity, limited bilateral hand movements, and the known spastic paraparesis. Eleven months after resuming chemotherapy, she presented with rapidly progressive upper extremity weakness and diurnal urinary incontinence, as well as severe pain requiring the use of opioid medication. She was admitted to the hospital for respiratory distress, at which time MRI revealed tumor progression and the development of perifocal edema (Fig. 1d). Antiepileptic treatment had to be initiated due to the onset of seizures despite the absence of abnormalities on cranial MRI. The patient was transferred to our institution for further surgical management. On arrival, she presented with impaired hand dexterity, limited bilateral hand movements, and spastic tetraparesis. After thorough discussion, we recommended surgical resection of the tumor recurrence due to clinical and radiologic progression, which occurred 17 months after the second recurrence and 13 months after initiation of palliative chemotherapy, respectively. We performed a re-laminoplasty (C2-C7) and a near total resection was achieved. Intraoperative ultrasound was used to determinate the tumor extent and guide resection. Surgery was performed under continuous neuromonitoring with standard measurements (D-wave as well as motor evoked potentials, direct nerve, and spinal cord stimulation). Electrophysiologic recordings remained unchanged throughout the surgery. Skin closure was performed with the Dermabond^® Prineo^® Skin Closure System [21]. Postoperative imaging confirmed near total resection of the tumor (Fig. 1e). A few days after surgery, the patient developed a cerebrospinal fluid fistula requiring operative wound revision and lumbar drain implantation. The wound remained dry thereafter. Perioperative ultra-rapid methylome analysis with nanopore sequencing [22, 23] revealed a high-grade neuroepithelial tumor (HGNET-MN1) consistent with astroblastoma. RNA sequencing of the tumor tissue showed evidence of an EWSR1 (exon 7)-BEND2 (exon 2) fusion. Histopathologic analysis revealed a Ki-67 proliferation index of 30–40%. The patient’s postoperative recovery was characterized by early mobilization to a wheelchair and progressive improvement of motor function in both hands and significant pain reduction. One week after revision surgery, the patient was able to resume one of her favorite activities – using a tablet. Early transfer to a pediatric rehabilitation center was arranged.

Since no molecular target was identified, and the disease thus far showed only relatively slow regrowth, there were no recommendations for immediate adjuvant therapy following the tumor board discussion involving neuro-oncologists from both centers involved in the patient management. Accordingly, the decision was made to follow up the tumor with radiologic imaging and clinical FU without any further adjuvant treatment and to perform an intensive rehabilitation program. Three months later, the FU MRI showed tumor progression (Fig. 1f). The patient experienced rapid clinical deterioration; she developed acute radiating pain and respiratory insufficiency while being treated by high-dose morphine for pain management. A decision was made to perform a cervical cord decompression, which provided significant pain relief. Ablation of the breathing tube was not possible due to insufficient breathing capacity. The following MRI showed a significant enlargement of the tumor with infiltration of the brainstem (Fig. 1g). The patient was offered palliative comfort care. One month after decompressive surgery, she showed complete tetraplegia, dependence on mechanical ventilation, and the ability to communicate through sounds, facial expressions, and eye movements. This raised significant ethical questions about how to proceed. A watchful waiting approach was adopted in conjunction with comfort care. The patient passed away 87 months after initial surgery.

We present a case of spinal astroblastoma in a 3-year-old child. To our knowledge, only 4 cases of spinal astroblastoma in children have been reported in the literature (Table 1). Because the tumor was initially – without molecular analyses – considered as ependymoma, our patient was treated according to the German strategy with HIT-SKK chemotherapy, local irradiation, and four cycles of vincristine-irinotecan-temozolomide after the first recurrence. With the increased accessibility of molecular diagnostic tools and the inclusion of molecular markers in the WHO classification of 2021, the diagnosis was refined to astroblastoma during the reexamination of initial tumor samples in Switzerland in 2022.

MN1-altered astroblastoma occurs mainly in children under the age of fifteen and has a marked female predominance [27]. They typically arise in the cerebral hemispheres and often present with seizures [27]. Spinal astroblastomas present with typical symptoms of intramedullary lesions, depending on the location, size, and growth rate of the tumor. Common symptoms include neck and back pain, sensory changes, motor weakness, bowel and bladder dysfunction, incoordination, spasticity, and pain.

Regardless of tumor location, the prognosis of MN1-altered astroblastoma is known to be poor. The 5- and 10-year progression-free survival rates for cerebral astroblastoma are 38% and 0%, respectively, while the 5- and 10-year overall survival rates are 89% and 55%, respectively [27]. No prognostic data are available for spinal cord astroblastoma due to the rarity of this entity. The progression-free survival of the few published pediatric cases is variable, even in children who have benefited from gross-total resection and adjuvant chemo- and radiotherapy. Of the four previously described cases of spinal astroblastoma in pediatric patients (Table 1), 1 case showed no recurrence at 6 months after gross-total resection (GTR) [26] followed by adjuvant temozolomide and intensity-modulated radiotherapy. In 2 cases where GTR could not be achieved, patients died at 1-month and 25-month FU, respectively [13, 24]. The latter patient showed tumor progression at 12 months after tumor biopsy and no adjuvant therapy was administered. In 1 case, no precise FU data were published [25]. Our case is the first describing long-term FU.

Despite the potential contribution of chemotherapeutic treatment in achieving long-term survival in our patient, eventual tumor progression resulted in an increase of motor disability, leading to a decline in the patient’s quality of life. This ultimately necessitated surgical resection to treat the neurological deficits. Surgery, established as the primary treatment for hemispheric astroblastoma, appears to have potential benefits and merits repetitive consideration in cases of spinal astroblastoma. Specialized care, particularly in dedicated centers with competent surgical and pathologic capabilities, is critical.

Microscopic examination of astroblastoma typically shows perivascularly arranged tumor cells with thick cell processes extending to a central hyalinized vessel, termed astroblastic pseudorosettes, which are also seen in other CNS tumors. According to cIMPACT-NOW recommendations, identification of MN1 fusion by next-generation sequencing or MN1 rearrangement by break-apart fluorescence in situ hybridization may be used to aid in the diagnosis of MN1-altered astroblastoma [28]. No formal tumor grade is assigned to astroblastoma in the 5th edition of the WHO CNS tumor classification [29]. Molecular diagnosis can be performed using ultra-fast tumor DNA methylation profiling based on nanopore sequencing [22, 23, 30]. Epigenetic analysis of tumor tissue is becoming increasingly important in personalized oncology and has recently been defined by the WHO as a standard of care in the classification of CNS tumors [31]. Genome-wide copy number profiles obtained in parallel with DNA methylation further contribute to molecular tumor diagnostics [32, 33]. Artificial intelligence-based methylome analysis and copy number profiling can rightly be considered the most advanced and clinically implemented branch of digital pathology [34]. While most routine diagnostic methylation profiling is performed on microarrays, only a few institutions are using same-day nanopore sequencing as an ultra-rapid alternative for both DNA methylation and copy number alteration detection. Nanopore sequencing has become one of the most powerful sequencing technologies since its development, enabling whole genome sequencing and disease diagnosis with high speed and cost-effective performance. Our institution uses nanopore sequencing coupled with ultra-fast supervised and unsupervised machine learning algorithms for complete methylome analysis and tumor classification within a few hours after tissue sampling [22]. This technology is of great interest in brain tumor surgery, where knowledge of the exact molecular diagnosis may have a direct impact on surgical strategy. Perioperative frozen section analysis by pathologists, which has been used to approximate the diagnosis, is prone to diagnostic error and lack of precision. Figure 2 shows the heterogeneity of the histopathologic presentation of astroblastoma, highlighting the importance of molecular diagnostics. The implementation of point-of-care tumor methylome analysis using nanopore sequencing, coupled with a locally developed epigenomic tumor diagnostic resource platform (EpiDiP/NanoDiP) [22], has the potential to revolutionize in-surgical decision making and also allow for a rapid transition to adjuvant therapy if needed. EpiDiP/NanoDiP is a comprehensive DNA methylation and copy number profiling suite designed as an open source, image-free digital pathology tool. This technology enables WHO-compliant methylome and copy number analysis even in low- and middle-income regions that may not have access to expensive technologies such as immunohistochemistry, conventional sequencing or array-based approaches to methylome profiling.

Due to the rarity of MN1-altered spinal astroblastoma, there are no detailed guidelines for the treatment of these tumors. We consider GTR to be the main treatment modality, allowing for improvement of neurological symptoms and reduction of tumor burden, thus improving the potential response to adjuvant therapies. Since astroblastoma is considered a glial tumor with a tendency to an aggressive course, some groups advocate the use of an adjuvant chemotherapy regimen with temozolomide, concomitant and subsequent to radiotherapy in cerebral astroblastoma [12]. Radiation doses up to 45 Gray can be safely used to treat spinal cord tumors in children. However, early recurrence has been described in the literature, and the treatment of these tumors remains challenging. Throughout the course of the disease, our patient underwent subtotal resection, biopsy, and near total resection of tumor recurrence, along with three different chemotherapy regimens and radiotherapy. These interventions contributed to long-term survival with improved quality of life.

In conclusion, spinal astroblastoma can present with different molecular signatures. To the best of our knowledge, this is the first published case of EWSR1-BEND2 fused spinal astroblastoma with long-term FU. EWSR1-BEND2 fused spinal astroblastoma is a rare tumor affecting children and adolescents. The few cases described in the literature showed recurrence after resection, adjuvant chemotherapy and radiotherapy. To enable potential targeted therapy in the future, further research into molecular targets is warranted.

Ethical approval is not required for this study in accordance with local or national guidelines. Written informed consent was obtained from a parent of the study participant to participate in the study. Written informed consent was obtained from a parent of the participant for the publication of the details of their medical case and any accompanying images.

The authors have no conflicts of interest to declare.

I.F.A. is enrolled in a fellowship in pediatric neurosurgery partially funded by a grant received by the André et Michel Bouriez Foundation. The funder had no role in the design, data collection, data analysis, and reporting of this study.

I.F.A.: first author. M.L., J.H., A.B., M.A., P.P., A.T., A.v.B., S.F., J.S.: contribution to the conception of the work, article review and approval of final version. R.G.: principal investigator, contribution to the conception of the work, article review, and approval of final version.

Due to the nature of the research, supporting data are not available. Further inquiries can be directed to the corresponding author.