GLOBULAR GLIAL FIBRILLARY ACIDIC PROTEIN-REACTIVE CYTOPLASMIC INCLUSIONS IN EPENDYMOMA - AN IMMUNOELECTRONMICROSCOPIC STUDY

We report of a 27-month-old boy with a recurrent infratentorial ependy moma; the initial resection was at 14 months of age. Both resection sp ecimens were histologically similar. In addition to neoplastic ependym al cells forming perivascular pseudorosettes, a second population of c ells with identical nuclear morphology displayed large hyaline, refrac tile cytoplasmic inclusions, causing these cells to superficially rese mble gemistocytic astrocytes. These inclusions demonstrated strong gli al fibrillary acidic protein (GFAP) immunoreactivity. Ultrastructurall y, the inclusions appeared as fenestrated irregular-shaped bodies with jagged edges and were made up of electron-dense granular material. Al though these inclusions superficially resembled Rosenthal fibers, immu noperoxidase stains for ubiquitin and alphaB-crystallin were negative. Immunoelectron microscopy showed that these unusual non-filamentous i nclusions were diffusely GFAP positive.