Astroblastoma with MN1::BEND2 in an elderly patient: A case report and review of the literature

Astroblastoma, MN1-altered, is a newly recognized type of primary central nervous system (CNS) tumor, which was included in the 2021 World Health Organization (WHO) classification [1]. MN1-altered CNS tumors are typically found in children, most often in females, displaying characteristic histological patterns without being pathognomonic. The most common fusion gene partner for MN1 is BEND2. Recent studies have reported circumscribed gliomas with EWSR1::BEND2 displaying the same morphological characteristics as astroblastomas with MN1::BEND2. [2] These were classified as methylation class (MC) astroblastoma, MN1-altered (previously named MC CNS HGNET-MN1), by the DKFZ DNA methylation classifier. They were clustered in close proximity to but distinct from the cluster of MN1-altered astroblastomas by t-SNE analysis. Therefore, in terms of molecular oncogenesis and tumor classification, BEND2 may have a greater impact than MN1; however, the rarity of these tumors hinders the availability of comprehensive clinical and outcome data. In addition, the lack of universally accessible molecular testing necessary for diagnosis poses a challenge in retrospectively collecting data. To date, few publications have provided information on clinical outcomes for patients diagnosed with astroblastoma in which fusion genes involving BEND2 were confirmed. …