The Cytogenetic Basis for Classifying Ependymomas

Abstract

The phylogeny of ependymal cells and astrocytes can be traced to a single primitive progenitor the ependymoglia or the tanycyte, respectively. Ependymoglia cells have ependymal perikarya having astrocyte-like processes that terminate subpially in primitive glial footplates. Such cells prevail in primitive nervous systems, but they also persist regionally in the mature mammalian brain. Their fine structure has been studied in many species. An electronmicroscopic study of 8 ependymomas reveals that the neoplastic cells possess features characteristic of primitive ependymoglia; in particular they possess cell processes filled with glial filaments, terminating submesenchymally in a primitive, piston-shaped footplate. The perivascular pseudorosettes of ependymomas are the equivalents of these cell poles. The dominant phenomenon of ependymoma structure appears to be a reversion of cellular organization to the stage of primitive ependymoglia cells. On reviewing 43 ependymomas and 71 astrocytomas 11 neoplasms were found having a tissue structure reminiscent of the evolution of piloid astrocytes from ependymoglia or tanycytes, respectively. These features correspond to transitional stages seen in normal primitive brains. Tumors of this type may be characterized as a tanycytic variant of ependymomas. They appear to be relatively common in the spinal cord and present a source of confusion with piloid astrocytomas.

9p21 and 13q14 dosages in ependymomas. A clinicopathologic study of 101 cases

“…It is also possible that the number of deletions is underestimated by the FISH technique (eg, small deletions or relative RB deletions in an extensively polyploid tumor). However, our frequencies of 9p and 13q losses are similar to those previously reported using other techniques 11,14,24,[32][33][34] and there appears to be no clear suggestion of a prognostic association based on the available data thus far. Therefore, it is probable that genes other than p16 and RB may be targeted by the 9p and 13q deletions in ependymomas.…”

“…11,21,24,[31][32][33][34] Based on the recent finding of CGH detectable losses in high-grade examples, it was suggested that the RB pathway may be specifically targeted in the process of tumor progression. 24 In contrast, our larger study similarly identified a subset of ependymomas with 9p or 13q deletions by FISH, but there were no obvious associations with tumor grade, location, patients age, recurrences, or death.…”

“…11 Measures of proliferative activity (Ki-67 labeling index) as well as p53, bcl-2, tenascin, vascular endothelial growth factor (VEGF) and epidermal growth factor (EGFR) protein expression levels have been correlated with tumor grade and clinical behavior, although none of these have become standard ancillary tools in routine diagnostic settings. 12,13 Chromosomal abnormalities have also been associated with tumor location, grade, and patient's age.…”

Intramedullary Subependymoma Occupying the Right Half of the Thoracic Spinal Cord. Case Report.

“…6) Only 27 cases of spinal subependymomas have been reported since 1954 (Table 1). [1][2][3][4][5]8,9,[11][12][13][14][16][17][18][19]21,23) The age of the patients ranged from 6 to 73 years, with the tumor found predominantly in men.…”

Spinal Tanycytic Ependymoma With Hematomyelia-Case Report-

“…7) Normal tanycytes are long nonbranching unipolar or bipolar cells that extend between the ventricular surface and the cortex. 1,4,[10][11][12] Tanycytes in the spinal cord surround the central canal, and radiate from the ependyma of the central canal into the gray matter. 12) Although the origin of the tanycyte remains unknown, electron microscopy has identified features suggestive of secretion and/or chemical transportation.…”