Case Report Low-grade neuroepithelial tumor: Unusual presentation in an adult without history of seizures Giulio Riva, 1 Luca Cima, 1 Manuela Villanova, 1 Claudio Ghimenton, 1 Sokol Sina, 1 Luca Riccioni, 2 Giada Munari, 3 Matteo Fassan, 3 Felice Giangaspero 4,5 and Albino Eccher 1 1 Pathology Unit, Department of Diagnostics and Public Health, University and Hospital Trust of Verona, Verona, 2 Pathology Unit, M. Bufalini Hospital, Cesena, 3 Surgical Pathology Unit, Department of Medicine (DIMED), University of Padua, Padua, 4 Department of Radiological, Oncological and Anatomo-Pathological Sciences, Sapienza University, Rome and 5 IRCCS Neuromed, Pozzilli, Molise, Italy Low-grade neuroepithelial tumors (LGNT) show a broad histopathological spectrum and may be difficult to classify using current World Health Organization (WHO) criteria. A 57-year-old man came to medical attention because of head- aches. The patient medical history was otherwise unremarkable. Magnetic resonance imaging (MRI) revealed a 2.5 cm lesion, partially cystic, with an increased signal on T2-weighted imaging, located in the right frontal lobe. The patient underwent right frontal craniotomy and the surgical specimen was entirely evaluated. Microscopic examination showed a tumor arranged predominantly in sheets and nests, with an infiltrative growth pattern and oligodendroglioma- like appearance. Tumor cells were round to oval with cyto- plasmic clearing, hyperchromatic nuclei and inconspicuous nucleoli. Only one mitosis was identified. Necrosis was absent. Differential diagnostic considerations included oligodendroglioma, clear cell ependymoma, polymorphous low-grade neuroepithelial tumor of the young (PLNTY) and long-term epilepsy-associated tumor with clear cell morphol- ogy. Neoplastic cells showed positivity for glial fibrillary acidic protein (GFAP), oligodendrocyte transcription factor 2 (OLIG2), α-thalasemia X-linked mental retardation syn- drome (ATRX) (retained nuclear expression) and CD34. Epithelial membrane antigen (EMA), neuronal nuclear anti- gen, microtubule-associated protein-2e, cyclo-oxygenase-2, chromogranin A and isocitrate dehydrogenase 1 (IDH1) (R132H) were negative. Ki-67 labeling index was 2–3%. Molecular analysis identified neither IDH1/IDH2 mutations nor 1p19q codeletion. Rapidly accelerated fibrosarcoma homolog B1 (BRAF) V600E mutation was also absent by both molecular and immunohistochemical testing. Polymer- ase chain reaction analysis revealed the presence of fibro- blast growth factor receptor 3 (FGFR3)-transforming acidic coiled-coil (TACC) fusion. Taken together, the morphologi- cal, immunohistochemical and molecular findings supported the final diagnosis of PLNTY. Key words: brain tumors, CD34, FGFR3-TACC3 fusion, low-grade neuroepithelial tumor, PLNTY. INTRODUCTION Epileptogenic tumors affecting children and young adults are neoplasms that exhibit varied histopathologic features and glial or glioneuronal differentiation. These tumors are also designated in the literature as long-term epilepsy- associated brain tumors (LeATs) or epileptomas. LeATs differ from most other brain tumors by early onset of spon- taneous seizures and frequent association with focal cortical dysplasia type IIIb. However, the broad neuropathologic spectrum and lack of reliable histopathological signatures make these tumors difficult to classify. 1 Instead, considering World Health Organization (WHO) 2016 classification, they can be diagnosed as pilocytic astrocytoma (PA), dif- fuse astrocytoma (DA), ganglioglioma (GG), pleomorphic xanthoastrocytoma (PXA), dysembryoplastic neur- oepithelial tumor (DNET), angiocentric glioma (AG), and oligodendroglioma (ODG). 2 Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a recently described variant of low-grade neuroepithelial tumor (LGNT), affecting children and young adults with seizures, characterized by the presence of oligodendroglioma-like cellular components, infiltrative growth pattern, and intense CD34 immunoreactivity. Moreover, PLNTYs exhibit a dis- tinct DNA methylation signature and frequent genetic abnormalities involving the genes for rapidly accelerated fibrosarcoma homolog B1 (BRAF), fibroblast growth factor Correspondence: Albino Eccher, MD, PhD, Department of Diagnos- tics and Public Health, Pathology Unit, P.le L. A. Scuro 10, 37134, Verona, Italy. Email: albino.eccher@aovr.veneto.it Received 16 April 2018; revised and accepted 03 July 2018; published online 26 July 2018. Neuropathology 2018; 38, 557–560 doi:10.1111/neup.12504 © 2018 Japanese Society of Neuropathology