Recurrent high-grade astroblastoma with MN1-BEND2 fusion in spinal cord and literature review.

Astroblastoma is an uncommon tumor of the central nervous system. It is variable in morphology, but the astroblastic pseudorosettes and vascular hyalinization are the most important features. Most astroblastomas occur in the cerebral hemisphere. We report a recurrent high-grade astroblastoma with MN1-BEND2 fusion in the spinal cord. Two lesions were found in the T5-7 level and T12-L1 level, and they were well defined in images. Rhabdoid and signet-ring-like cells were observed. It may be classified as a high-grade tumor due to cellularity, high mitotic count, and pleomorphism. The tumor cells were diffusely positive for GFAP, Olig-2, and S-100 protein. We found the MN1 arrangement and the loss of chromosome 1p by FISH, and further validated the BEN domain containing 2 genes (BEND2), which is the fusion partner of meningioma 1 gene (MN1), by next-generation sequencing (NGS) and Sanger sequencing. The MN1 mutation is crucial in the diagnosis and prognosis of rare astroblastoma. The spinal cord astroblastoma may have a high recurrence rate because of the residual lesion at the unique location and higher grade; the connection with the gene mutation is unclear. Regular follow-up is necessary. Further study and more cases are needed to establish evidence for diagnosis, prognosis, and treatment of astroblastoma with molecular characteristics.