Rosenthal fibers are -

A Rosenthal fiber is a thick, elongated, worm-like or "corkscrew" eosinophilic (pink) bundle that is found on H&E staining of the brain in the presence of long-standing gliosis, occasional tumors, and some metabolic disorders. ASSOCIATED CONDITIONS Its presence is associated with either pilocytic astrocytoma(more common) or Alexander's disease (a rare leukodystrophy). They are also seen in the context of fucosidosis. COMPOSITION The fibers are found in astrocytic processes and are thought to be clumped intermediate filament proteins. Their components include glial fibrillary acidic protein. Ref: Wikipedia