Since the appearance in 2000 of the World Health Organization (WHO) classification for central nervous system (
CNS) neoplasms, numerous descriptions of new entities or variants have appeared in the literature. In the group of neuronal and mixed glioneuronal
neoplasms are lesions with distinctive morphological features that are still not included in a precise classification, including extraventricular
neurocytoma, papillary glioneuronal
tumor, rosette-forming glioneuronal of the fourth ventricle, glioneuronal with neuropil-like rosette, and
DNT-like
tumor of the septum pellucidum. The glioneuronal
tumor with neuropil-like rosette and
oligodendroglioma with neurocytic differentiation represent morphological variants of genetically proven diffuse
gliomas. The lipoastrocytoma and the pilomixoid
astrocytoma enlarge the group of astrocytic lesions. Rare, low-grade
gliomas of the spinal cord with extensive leptomeningeal dissemination associated with unusual neuroimaging are described. The chordoid
glioma of the third ventricle and the papillary
tumor of the pineal region seem to be correlated by a common histogenesis from the specialized ependyma of the subcommissural organ. An embryonal
tumor with neuropil and true rosettes combining features of
neuroblastoma and
ependymoblastoma is discussed. These new, recently described lesions indicate that the complex morphologic spectrum of CNS
tumors is far from being completely delineated.