Rosenthal fiber

Dense granular and osmiophilic inclusions within astrocyte processes and cell bodies, which are surrounded by glial filaments and composed of glial fibrillary acidic protein, the small heat shock proteins, alphaB-crystallin and HSP27, and ubiquitin. Their widespread distribution in Alexander disease includes prominent subpial and subependymal as well as perivascular locations. Rosenthal fibers also occur in tumors, hamartomas, and other conditions.