OBJECTIVE: To describe the pathological features of three very similar and unusual primary @entity1221 that are not readily recognized as @entity424 but which, by ultrastructural examination, have an ependymomatous character. METHODS: Three distinctive @entity5 were found in a review of our files for cases of @entity424 . In each case, @entity1710 and @entity1711 -stained sections were reviewed, and immunostains for epithelial membrane antigen, cytokeratin, @entity2277 , and glial fibrillary acidic protein were performed on @entity406 -fixed, @entity982 -embedded sections. Electron microscopy was performed in each case. RESULTS: The @entity5 had a diffuse myxoid background, often containing tightly clustered cells that mimicked multinucleated giant cells, but lacking perivascular pseudorosettes or central lumen rosettes. Glial fibrillary acidic protein and @entity2277 immunostains did not reveal perivascular processes. Epithelial membrane antigen immunostains showed a dot-like cytoplasmic immunoreactivity in some cell clusters in two of the three cases. Cytokeratin was negative in all three cases. However, ultrastructurally, the cells of each @entity5 had extensive surface microvilli; the giant cell-like clusters had cells with extensive close appositions, some junctions, and, in two cases, lumina with microvilli. Two of the @entity1 were adults (both with @entity1315 ), and one @entity1 was 13 years old and had a cervical spinal cord intramedullary @entity5 . Each @entity5 was sharply circumscribed from adjacent central nervous system tissue but was not encapsulated. One of the cases in an adult was mitotically highly active; this @entity5 recurred locally 4 years after initial gross total excision. CONCLUSION: These @entity5 are unusual variants of @entity424 . This pattern of @entity424 is sufficiently distinctive to be recognized in @entity1710 and @entity1711 stains once the architecture of the epithelioid clusters is appreciated.

XXXX : a new variant of @entity424 : report of three cases.

@entity1 :: ('9606', 'Species') :: ['patients', 'patient'] @entity424 :: ('MESH:D004806', 'Disease') :: ['ependymoma', 'conventional ependymomas'] @entity5 :: ('MESH:D009369', 'Disease') :: ['tumor', 'tumors'] @entity1711 :: ('MESH:D004801', 'Chemical') :: ['eosin'] @entity1221 :: ('MESH:D016543', 'Disease') :: ['central nervous system tumors'] @entity406 :: ('MESH:D005557', 'Chemical') :: ['formalin'] @entity1710 :: ('MESH:D006416', 'Chemical') :: ['hematoxylin'] @entity982 :: ('MESH:D010232', 'Chemical') :: ['paraffin'] @entity2277 :: ('7431', 'Gene') :: ['vimentin'] @entity1315 :: ('MESH:D004833', 'Disease') :: ['temporal lobe tumors']
@entity424 :: (MESH:D004806,Disease) :: ['Epithelioid ependymoma']
