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High-grade supratentorial tumors harboring ZFTA::NCOA1/2 fusion in infants presenting with mixed histology of embryonal-appearing components resembling ependymoma and mesenchymal sarcomatous components have recently been reported as ependymoma-like tumors with mesenchymal differentiation (ELTMDs). In contrast, we describe herein a pathologically similar case with a novel ZFTA::RELA fusion in an adult. A frontal lobe lesion was resected from a 30-year-old woman and displayed mixed components on pathological examination, showing ependymoma-like and sarcomatous parts. The absence of perivascular pseudorosettes was inconsistent with a diagnosis of ependymoma. Fluorescence in situ hybridization analysis confirmed ZFTA::RELA fusion. The DKFZ methylation classifier (v12.8) did not categorize this case among established methylation classes. In addition, t-distributed stochastic neighbor embedding analysis using DNA methylation data revealed that the present case was distant from ependymomas but close to two previously reported cases of ELTMD involving ZFTA::NCOA1/2 fusion. Taken together, we concluded that this tumor should be considered under the entity of ELTMD. This represents the first description of an adult patient with ELTMD harboring ZFTA::RELA fusion analyzed by DNA methylation profiling, supporting the establishment of ELTMD as a possible new tumor type., (© 2024. The Author(s), under exclusive licence to The Japan Society of Brain Tumor Pathology.)

Ancient schwannoma (AS) is a subtype of schwannoma characterized by slow progression despite degenerative changes in pathology. Although it is considered a benign tumor, most previous reports have focused on extracranial AS; therefore, the clinical characteristics of intracranial AS is not clear. We included 174 patients who underwent surgery for sporadic intracranial schwannoma, and 13 patients (7.5%) were diagnosed with AS. Cysts were significantly more common in patients with AS than conventional schwannomas (92.3% vs. 44.7%, p < 0.001), as was bleeding (38.5% vs. 6.9%, p = 0.003) and calcification (15.4% vs. 1.3%, p = 0.029). The maximum tumor diameter was also larger in patients with AS (35 mm vs. 29 mm, p = 0.017). The median duration from symptom onset to surgery (7.0 vs. 12.5 months, p = 0.740) did not significantly differ between groups, nor did the probability of postoperative recurrence (p = 0.949). Intracranial AS was strongly associated with cyst formation and exhibited a benign clinical course with a lower rate of recurrence and need for salvage treatment. Extracranial AS is reportedly characterized by a slow progression through a long-term clinical course, whereas intracranial AS did not progress slowly in our study and exhibited different clinical features to those reported for extracranial AS., (© 2024. The Author(s).)

Central neurocytoma (CN) is classically defined by its intraventricular location, neuronal/neurocytic differentiation, and histological resemblance to oligodendroglioma. Extraventricular neurocytoma (EVN) shares similar histological features with CN, while it distributes any site without contact with the ventricular system. CN and EVN have distinct methylation landscapes, and EVN has a signature fusion gene, FGFR1-TACC1. These characteristics distinguish between CN and EVN. A 30-year-old female underwent craniotomy and resection of a left intraventricular tumor at our institution. The histopathology demonstrated the classical findings of CN. Adjuvant irradiation with 60 Gy followed. No recurrence has been recorded for 25 years postoperatively. RNA sequencing revealed FGFR1-TACC1 fusion and methylation profile was discrepant with CN but compatible with EVN. We experienced a case of anatomically and histologically proven CN in the lateral ventricle. However, the FGFR1-TACC1 fusion gene and methylation profiling suggested the molecular diagnosis of EVN. The representative case was an "intraventricular" neurocytoma displaying molecular features of an "extraventricular" neurocytoma. Clinicopathological and molecular definitions have collided in our case and raised questions about the current definition of CN and EVN., (© 2023. The Author(s).)

"Oligoastrocytoma" disappeared as of the revised fourth edition of the World Health Organization Classification of Tumours of the Central Nervous System, except where appended with "not otherwise specified (NOS)". However, histopathological and genetic backgrounds of cases with dual features of astrocytoma/oligodendroglioma have been sparsely reported. We encountered a 54-year-old man with right frontal glioma comprising two distinct parts on imaging and histopathological examination: grade 4 astrocytoma with IDH1-R132H, ATRX loss, p53-positivity and intact 1p/19q; and oligodendroglioma with IDH1-R132H, intact ATRX, p53-negativity and partially deleted 1p/19q. At recurrence, histopathology showed low-grade mixed astrocytic and oligodendroglial features: the former with IDH1-R132H, ATRX loss, p53-positivity and intact 1p/19q and the latter showing IDH1-R132H, intact ATRX, p53-negativity and 1p/19q codeletion. At second recurrence, histopathology was astrocytoma grade 4 with IDH1-R132H, ATRX loss, p53-positivity and intact 1p/19q. Notably, 1p/19q codeletion was acquired at recurrence and CDKN2A was deleted at second recurrence. These findings suggest insights into tumorigenesis: (1) gliomas with two distinct lineages might mix to produce "oligoastrocytoma"; and (2) 1p/19q codeletion and CDKN2A deletion might be acquired during chemo-radiotherapy. Ultimately, astrocytic and oligodendroglial clones might co-exist developmentally or these two lineages might share a common cell-of-origin, with IDH1-R132H as the shared molecular feature., (© 2022. The Author(s), under exclusive licence to The Japan Society of Brain Tumor Pathology.)

Cerebellar liponeurocytoma is a rare tumor that usually develops in adult patients, and is categorized as World Health Organization grade II. Because of the small number of reports on its radiological and pathological features, the disease remains poorly characterized. The current case involved a 59-year-old man with tumor in the upper cerebellar vermis. Preoperative positron emission tomography (PET) showed high uptake on (11)C-methionine PET, but low uptake on (18)F-fluorodeoxyglucose PET. These findings resemble those of central neurocytoma and oligodendroglioma, but are incompatible with other brain tumors. Subtotal tumor removal was performed by suboccipital craniotomy. Histopathological examinations showed sheets of small, isomorphic cells with round nuclei and clear cytoplasm, and focal vacuolated cells resembling adipose cells. On immunohistochemistry, tumor cells were positive for synaptophysin and NeuN. Vacuolated cells were immunoreactive for perilipin. Based on these findings, cerebellar liponeurocytoma was diagnosed. Genetic analyses revealed absences of both chromosome 1p/19q loss and isocitrate dehydrogenase 1 mutation, further ruling out oligodendroglioma. These radiological and genetic aspects of cerebellar liponeurocytoma, which are mostly in common with central neurocytoma, should prove helpful in differentiating this rare tumor from other tumors with similar morphology.