Ependymoblastoma: dear, damned, distracting diagnosis, farewell!* - PubMed (original) (raw)

Ependymoblastoma: dear, damned, distracting diagnosis, farewell!*

Alexander R Judkins et al. Brain Pathol. 2010 Jan.

Abstract

Ependymoblastoma is a diagnostic label that has been applied to a variety of rare central nervous system (CNS) tumors over the last eight decades. Consequently, there is uncertainty about whether such an entity exists and what its characteristic features might be. The current study, based on 14 cases from our institutional archives and identified by the search terms "ependymoblastoma,"ependymoblastomatous," "ependymoblastic" or "PNET with ependymal differentiation," aimed to test the hypothesis that the ependymoblastoma is a distinct and recognizable entity. Ependymoblastic rosettes are a key diagnostic feature and were present in 11/14 (79%) tumors, eight (73%) of which were embryonal tumors with abundant areas of neuropil-like differentiation. Three other cases showed rare ependymoblastic rosettes in the histopathological setting of a typical primitive neuroectodermal tumor (PNET), medulloblastoma (MB) or atypical teratoid/rhabdoid tumor (AT/RT). The remaining cases were all embryonal tumors with structures that mimicked ependymoblastic rosettes. Our results indicate that ependymoblastic rosettes are most frequently encountered in embryonal tumors with abundant neuropil and less frequently in other CNS embryonal neoplasms, including PNET, MB and AT/RT. We believe that ependymoblastoma as a diagnosis is neither precise nor specific and that it is time once and for all to retire this diagnosis from the lexicon of neuropathology.

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Figures

Figure 1

Figure 1

Embryonal tumor with abundant neuropil and ependymoblastic rosettes. Ependymoblastic rosettes form conspicuous concentric cellular rings that appear as islands in neoplastic neuropil (A). Ependymoblastic rosettes forming distinctive multilayered structures with a small round central lumen bounded an internal limiting membrane. Cells along the outer edge of the rosette merge into the surrounding neuropil and embryonal tumor cells. Mitotic activity is prominent in the walls of the rosettes (B). Immunohistochemical staining for epithelial membrane antigen highlights the limiting membrane of the central lumen (C). Immunohistochemical staining for Ki‐67 highlights the proliferative activity within rosettes (D). Immunohistochemical staining for NFP highlights abundant intervening neoplastic neuropil as well as demonstrating cytoplasmic expression in many of the embryonal cells (E). Immunohistochemical staining for neuronal nuclei antigen highlights scattered cells with more advanced neurocytic differentiation within the neoplastic neuropil (F).

Figure 2

Figure 2

Other embryonal tumors with ependymoblastic rosettes. Embryonal tumor with areas of neuropil‐like differentiation and small ependymoblastic rosettes (A). Focal epithelioid differentiation in neoplastic cells (B). Focal germ cell (yolk sac) differentiation (C). Immunohistochemical staining for cytokeratin (D), alpha‐fetoprotein (E) and INI1 (F).

Figure 3

Figure 3

Structures that mimic ependymoblastic rosettes. Tumors with neuropil differentiation and prominent perivascular cellular collars that resemble ependymoblastic rosettes (A,B). Highly cellular tumor with myxoid vascular degeneration giving rise to structures that resemble ependymoblastic rosettes but which lack internal limiting membrane (C). Immunohistochemical staining for collagen type IV of same tumor highlights the blood vessels giving rise to this appearance (D).

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