A Pediatric Tumor Found Frequently in the Adult Population: A Case of Anaplastic Astroblastoma in an Elderly Patient and Review of the Literature

A Rare Case of a High-Grade Astroblastoma with 5-Year Follow-up

Astroblastoma is a very rare glial tumor derived from astroblasts. It has been controversial in terms of its features and diagnosis. The objective of this report is to present the findings of the high-grade astroblastoma with a good prognosis in a 21-year-old female who presented to us with diplopia and headache. While imaging led to the foremost differentials of pleomorphic xanthoastrocytoma and Ganglioglioma which are low-grade neoplasms, the final diagnosis was established on microscopy and immunohistochemistry after excision. Treatment protocol included surgery with postoperative radiotherapy and chemotherapy. Due to controversial and limited literature, this tumor poses difficulties in diagnosis and management. This is a rare, successfully managed case of astroblastoma with a positive outcome 5 years after the diagnosis was established. In this case report, we review the steps of diagnosis, the differentials, the pathological and histological features, and the management of this rare entity.

A case report of high-grade astroblastoma in a young adult

Astroblastoma is an uncommon neuroepithelial primary tumor of the brain which is of uncertain origin. We present a case of high-grade astroblastoma in an 18-year-old female with a severe headache, loss of appetite, vomiting and generalized weakness. The patient had undergone a right frontoparietal craniotomy. Large subfalcine meningioma was excised. The lesion was suspected to be a meningioma. Primary radiological investigation revealed a 6.8 cm × 5.8 cm × 5.4 cm lesion. Although the radiological and intraoperative findings were of an extra-axial tumor, the histology and immunophenotype was of an astroblastoma. The patient was treated with cyclophosphamide, cisplatin and etoposide chemotherapy regimen. The patient was later treated with bi-weekly bevacizumab. The patient had improved symptomatically post-chemotherapy. However, there was no significant difference in lesion size. The patient died after 2 weeks. The prognosis of patients with astroblastoma is extremely poor as observed in our case.

Multimodal molecular analysis of astroblastoma enables reclassification of most cases into more specific molecular entities

Astroblastoma is a rare and controversial glioma with variable clinical behavior. The diagnosis currently rests on histologic findings of a circumscribed glioma with astroblastomatous pseudorosettes and vascular hyalinization. Immunohistochemical studies have suggested different oncogenic drivers, such as BRAF p.V600E, but very few cases have been studied using genome-wide methodologies. Recent genomic profiling identified a subset of CNS embryonal tumors with astroblastoma-like morphology that harbored MN1 gene fusions, termed "CNS high-grade neuroepithelial tumors with MN1 alteration" (CNS-HGNET-MN1). To further characterize the genetic alterations that drive astroblastomas, we performed targeted next-generation sequencing (NGS) of 500 cancer-associated genes in a series of eight cases. We correlated these findings with break-apart fluorescence in situ hybridization (FISH) analysis of the MN1 locus and genome-wide DNA methylation profiling. Four cases showed MN1 alteration by FISH, including two pediatric cases that lacked other pathogenic alterations, and two adult cases that harbored other cancer-associated gene mutations or copy number alterations (eg, CDKN2A/B homozygous deletion, TP53, ATM and TERT promoter mutations). Three of these cases grouped with the CNS-HGNET-MN1 entity by methylation profiling. Two of four MN1 intact cases by FISH showed genetic features of either anaplastic pleomorphic xanthoastrocytoma (BRAF p.V600E mutation, CDKN2A/B homozygous deletion and TERT promoter mutation) or IDH-wildtype glioblastoma (trisomy 7, monosomy 10, CDK4 amplification and TP53, NRAS and TERT promoter mutations) and these cases had an aggressive clinical course. Two clinically indolent cases remained unclassifiable despite multimodal molecular analysis. We conclude that astroblastoma histology is not specific for any entity including CNS-HGNET-MN1, and that additional genetic characterization should be considered for astroblastomas, as a number of these tumors likely contain a methylation profile or genetic alterations that suggest classification as other tumor entities. Our heterogeneous molecular findings help to explain the clinical unpredictability of astroblastoma.