Prognostic factors in central neurocytomas: a multicenter study of 71 cases.

Central neurocytoma (CN) is a rare intraventricular tumor presenting a benign histologic appearance and favorable prognosis after surgery. In contrast, "atypical" CN is defined by a high MIB1 proliferation index and/or histologic features of malignancy, which are associated with a poorer outcome. This variant of CN remains somewhat controversial. To better characterize CN and its "atypical" variant, a retrospective multicenter study was conducted on 71 patients presenting with CN. A statistical analysis of clinical, radiologic, and histologic data was conducted to validate prognostic factors. The immunohistochemical phenotype of CNs, analyzed by tissue microarrays, and the MIB1 index were evaluated for 45 cases. Tissue microarrays validated the expression of neuronal markers synaptophysin and NeuN, but not that of glial markers glial fibrillary acidic protein and oligodendrocyte transcription factor 2. In the univariate analysis, a tumor volume ≥30 cm (P=0.025), incomplete surgery (P=0.033), and a mitotic count ≥3 per 10 high-power fields (P=0.009) were predictors of a higher risk of recurrence, unlike the other usual histologic features of malignancy and the high MIB1 index. Partial surgery was the only criterion associated with a poorer outcome in the multivariate model. Our results, based on a large multicenter series, show the striking homogeneity of CNs and do not support the use of histologic criteria as reliable markers to define an "atypical" group of CNs. Our study suggests that the extent of surgery is the main factor to be considered in the prognostic assessment of patients with CN.