Multinodular and vacuolating neuronal tumor: molecular genetics and DNA methylation analysis of 12 cases.

Multinodular and vacuolating neuronal tumor (MVNT) was recognized as a distinct neuronal tumor entity in the revision of the 2021 World Health Organization (WHO) Classification of Tumors of the CNS. In this study, we retrospectively analyzed 12 surgical cases, two of which exhibited ganglioglioma (GG)-like components. The cohort consisted of eight male and four female patients, with a median age of 31 years (age range: 18-53 years). Seizures were the most common clinical presentation, followed by headache and dizziness. Three patients were incidentally identified during physical examination. Ten tumors were located in the cerebral hemisphere, and the remaining two were found in the cerebellum and thalamus, respectively. Histopathological examination revealed clusters of neuroepithelial cells with large amphophilic vacuolated cytoplasm and eccentrically placed round nuclei containing prominent nucleoli. Immunohistochemically, these vacuolated cells were positive for OLIG2, MAP2, SYN and SOX10, and negative for GFAP and NEUN. DNA sequencing analysis identified no mutations in IDH1, IDH2, BRAF V600E, TERT promoter, or EGFR genes. Among the cohort, three cases harbored FGFR2 mutations, and FGFR2::INA gene fusion was detected in both MVNT and GG-like components. Two cases carried BRAF mutation, and one case exhibited MAP2K1 mutation. A novel BCAN::NTRK1 (exon 12-exon 9) gene fusion was identified in one case. DNA methylation profiling of eight cases revealed that none matched with a known CNS tumor type. Six cases formed a separate methylation cluster, suggesting a potential novel molecular subtype, while the remaining two cases exhibited transcriptional similarities to supratentorial pilocytic astrocytoma and rosette-forming glioneuronal tumor (RGNT), respectively. Postoperatively, all patients remained seizure free with no evidence of tumor progression. Only one patient died 16 months after surgery due to an unrelated traffic accident. © 2026 The Pathological Society of Great Britain and Ireland.