Origin of chordoid glioma of the third ventricle.

Context: Chordoid glioma is a relatively recently described unique glial neoplasm that has been formally codified by the World Health Organization in Pathology and Genetics of Tumours of the Nervous System, in which it is included along with astroblastoma and gliomatosis cerebri under the rubric "Tumors of Uncertain Origin." Many examples of chordoid glioma come to clinical attention only at a relatively large size and occupy a large portion of the third ventricle. Accordingly, the anatomic origin of chordoid glioma has been unclear and debated.

Objective: To examine the regional anatomic origin of chordoid glioma.

Data Sources: The clinical, imaging, histologic, immunophenotypic, and ultrastructural data in previously published case series and individual case reports of chordoid glioma were reviewed in conjunction with the study of a new case of chordoid glioma that presented at a relatively small size, thereby facilitating neuroanatomic localization.

Conclusions: Chordoid glioma exhibits features of specialized ependymal differentiation on ultrastructural examination, and all examples reported in the literature to date have displayed a highly stereotypical suprasellar anatomic localization and an ovoid shape, as seen on neuroimaging studies and gross anatomy. Neuroanatomic, radiologic, and clinical evidence supports an anatomic origin for chordoid glioma from the vicinity of the lamina terminalis.