Extraventricular neurocytomas stratified by tumor location and histological subtype: clinical features, radiology, pathology, and prognosis

Abstract

Abstract Objective To compare the differences in clinical manifestations, imaging features, histological characteristics, and prognostic outcomes of extraventricular neurocytomas (EVNs) based on tumor location (parenchymal vs. sellar) and histological subtype (typical vs. atypical). Methods A retrospective analysis was performed on 28 patients with pathologically confirmed EVNs from three hospitals between January 2010 and March 2025 (17 parenchymal, 11 sellar; 15 typical, 13 atypical). Clinical, radiological, histopathological, and follow‑up data were collected. Data analysis for this study began in January 2026. Atypical EVNs were defined by a Ki‑67 labeling index > 5% or the presence of any of the following histological features: brisk mitotic activity (> 5 per 10 HPF), necrosis, or microvascular proliferation. Continuous variables were compared using the t‑test or non‑parametric test, and categorical variables using the χ² test or Fisher’s exact test, as appropriate. Survival curves were estimated using the Kaplan–Meier method, and between‑group comparisons were performed using the log‑rank test. A two‑tailed P value < 0.05 was considered statistically significant. Results Patients with parenchymal EVNs were significantly younger than those with sellar EVNs (25.29 ± 17.32 vs. 49.09 ± 10.25 years, P < 0.001). Parenchymal EVNs showed a larger tumor diameter compared with sellar EVNs(37 vs. 22 mm, P =0.043). Parenchymal EVNs commonly presented with headache and seizures, whereas sellar EVNs presented with visual decline. On MRI, parenchymal EVNs were predominantly cystic‑solid with septation, calcification, and peritumoral edema, while sellar EVNs were homogeneously solid, showed marked enhancement, and lacked edema. All tumors expressed synaptophysin. The glial fibrillary acidic protein (GFAP) positivity rate was significantly higher in parenchymal than in sellar EVNs (76.5% vs. 18.2%, P = 0.006). Gross total resection (GTR) was achieved in all parenchymal EVNs (100%) but in only 27.3% of sellar EVNs. During follow-up, 7 of 28 patients experienced recurrence or progression(PFS event). Atypical EVNs showed a tendency toward earlier recurrence or progression (range 12–84 vs. 16–102 months), although the event rate was numerically lower in the atypical group than in the typical group (23.1% vs. 26.7%, P > 0.999). Atypical EVNs also received upfront adjuvant radiotherapy more frequently than typical EVNs (30.8% vs. 0.0%, P = 0.035).The 1-year and 2-year PFS rates for the entire cohort were 93.8% and 79.3%, respectively. The log-rank test revealed no significant difference in PFS between parenchymal and sellar EVNs ( P = 0.363) or between typical and atypical EVNs ( P = 0.682). Conclusions Parenchymal and sellar EVNs exhibit distinct profiles in age at onset, clinical presentation, and imaging features, with the striking GFAP expression difference further supporting this biological heterogeneity and aligning with the emerging glioneuronal tumour with neurocytic differentiation (GNTN) molecular framework. Sellar EVNs have a low GTR rate and warrant closer postoperative imaging surveillance. Atypical EVNs—defined by Ki‑67 > 5% or histologically aggressive features—show a tendency toward earlier recurrence/progression and more frequent upfront adjuvant radiotherapy use; however, the present results neither refute the established prognostic distinction between typical and atypical EVNs reported in previous studies, nor support the conclusion that the two subtypes have comparable outcomes.No significant effect of tumor location or histological subtype on PFS was observed; however, the small sample size limits interpretation of these negative findings. Future multicenter studies incorporating molecular profiling are needed to refine risk stratification.