XXXX of the third ventricle: a report of two new cases, with further evidence supporting an ependymal differentiation, and review of the literature.

@entity1 @entity424 @entity39 @entity75 @entity5 @entity11 @entity2277 @entity1758 @entity2280 @entity204 @entity2281
The term @entity11 of the third ventricle was first used to describe a rare and slowly growing @entity5 of uncertain histogenesis, with chordoid appearance, occurring preferentially in middle-aged @entity1 . Herein we report two additional examples of this novel entity together with a literature review based on the 25 cases previously published. Our review fully confirms the strikingly stereotyped clinical, neuroradiologic, and pathologic features of this unique @entity5 . The female/male ratio was 1.7:1, and the age range was 24-70 years (mean 44.9 years). In all 27 cases imaging findings were similar showing a well-defined mass (mean 2.8 cm in largest dimension), ovoid in shape, hyperdense on CT scans, with uniform and intense contrast enhancement, arising in the hypothalamic/suprasellar/third ventricular region. Histologically, the main consistent characteristics were cords and clusters of epithelioid cells within an abundant mucinous and often vacuolated background. Mitoses were sparse or absent and anaplastic features, endothelial proliferation, and @entity39 were not identified. Lymphoplasmacytic infiltrates with Russell bodies were frequent throughout the @entity5 and its interface with adjacent @entity75 . Most of the @entity5 cells revealed a strong and diffuse expression of @entity2277 and glial fibrillary acidic protein. Additionally, the vast majority of @entity5 showed focal coexpression of cytokeratins, @entity2280 , @entity2281 protein, and epithelial membrane antigen; the @entity1758 labeling indices were uniformly low. Surprisingly for a @entity11 assigned WHO grade II, the 19 @entity1 with an available but short follow-up (mean 22.5 months; range 6-68 months) experienced a rather poor outcome (three recurrences and seven @entity204 ), probably reflecting the anatomic site of the @entity5 that precludes a complete surgical excision rather than its histologic composition. Ultrastructural examination of 10 cases demonstrated findings in line with a glial derivation and a putative ependymal origin such as cytoplasmic intermediate filaments, microvilli, intermediate junctions or desmosomes, and focal basal lamina formation. In our case no. 1, and for the first time in this @entity5 , we observed sparse and abnormal cilia in an aberrant juxtanuclear location, a further argument for considering @entity11 as a subtype of @entity424 . However, a better understanding of the biologic behavior and histogenesis of this distinctive clinicopathologic entity needs to be investigated with a larger series. Nevertheless, taking into account its strikingly consistent anatomic localization, its unique histopathologic and immunohistochemical profile, in conjunction with the most recent and convincing ultrastructural arguments, we suggest that @entity11 of the third ventricle could be better classified as @entity424 of the lamina terminalis area.
