So-called malignant and extra-ventricular neurocytomas: reality or wrong diagnosis? A critical review about two overdiagnosed cases.

Central neurocytoma (CN) is described as a rare intra-ventricular benign neuronal tumor of the brain. Two primary tumors first diagnosed as malignant and extra-ventricular neurocytomas are reported here. Histologically, the tumor of the first patient, a forty-one-year-old man, consisted of monotonous cells with round nuclei, but no fibrillar background. The second tumor, in a nineteen-year-old girl, showed areas of moderately pleomorphic round cells, with numerous rosettes and ganglion cell differentiation, in an abundant fibrillary network. Both presented calcifications. Mitoses were more frequent in recurrences and spinal locations than in the primaries. All tumors stained strongly for synaptophysin, and GFAP was partly positive in the first case only. Patients received post-surgical radiotherapy and were still alive eight and six years, respectively, after initial surgery. The interpretation of atypical cases, such as ours is not easy: the diagnoses finally retained were oligodendroglioma in the first case and ganglioneuroblastoma in the second case. Furthermore, neurocytomas atypical either by their unusual topographical or histological presentation or by their poor prognosis, have been frequently entitled in this way on synaptophysin positivity. So, we were prompted to reassess the entity of CN, seventeen years after the first description, to re-appreciate the reality of anatomo-clinical variants and to discuss the value of synaptophysin positivity in these tumors. In conclusion, it seems preferable to individualize true classical CN, which has a favorable outcome, from so-called extra-ventricular, atypical and anaplastic, clinically malignant neurocytomas for which complementary treatment is required.