Neuroepithelial tumor with EWSR1-BEND2 fusion: Case report and review of literature
Vijayanarayanan A, Chitale D, Keller C, and Mukherjee A. Neuroepithelial tumor with EWSR1-BEND2 fusion: Case report and review of literature. J Neuropathol Exp Neurol 2022; 81(6):493.
J Neuropathol Exp Neurol
A 26-year-old female initially presented at an outside institution with migraines and blurry vision four years ago. Imaging revealed a 4.5 cm frontal lobe mass. Pathology of the mass was consistent with a poorly differentiated epithelial neoplasm with focal neuroendocrine features. She underwent extensive but unsuccessful workup in search of a possible primary lesion. The patient declined radiation to the tumor bed at that time. Three years later, her symptoms advanced to bilateral blindness. Imaging of her brain showed progression of the disease with multifocal enhancing masses. Reexcision in our institution showed a cellular and circumscribed neoplasm composed of small to medium cells in nests and interconnected follicular/cribriform structures with luminal eosinophilic material. The tumor cells showed strong and diffuse immunoreactivity for epithelial markers (EMA, Cam5.2) and patchy immunoreactivity to CD56 while being negative for all neural and glial markers including synaptophysin and GFAP. The MIB-1 proliferation index was 3%. FISH for isochromosome 12p was negative. NGS analysis revealed an in frame fusion of exon 7 of Ewing sarcoma breakpoint region 1 gene (EWSR1) on chromosome 22 with exon 2 of BEN domain containing 2 (BEND2) on chromosome X as a result of t(X; 22) (p22; q12). This novel fusion has been identified in subsets of astroblastomas in spinal cord, brain stem and cerebrum. This tumor, while circumscribed, did not show astroblastoma like rosettes or hyalinization. There was no immunohistochemical evidence of glial or neuronal differentiation. The prominent epithelial differentiation led to an exhaustive but unsuccessful search for a primary. Our case adds to the spectrum of morphological and immunohistochemical findings seen in this emerging group of tumors.