CYTOPLASMIC INCLUSIONS OF ASTROCYTIC ELEMENTS OF GLIAL TUMORS - SPECIAL REFERENCE TO ROUND GRANULATED BODY AND EOSINOPHILIC HYALINE DROPLETS

Round granulated body (RGB) and eosinophilic hyaline droplets (EHDs) h ave been described as cytoplasmic inclusions of certain astrocytic tum ors. In the previous literature, however, these inclusions have been d escribed using various terms or regarded as nosologically the same ent ity. Light microscopically, RGB appeared as a round discrete body fill ed with fine uniform granules, while EHDs demonstrated a cluster of br ight eosinophilic, round objects of various size. They could be clearl y distinguished even by conventional histochemical staining such as th e Masson trichrome stain and the phosphotungstic acid hematoxylin prep aration. Both RGB and EHDs expressed positive immunoreactions for glia l fibrillary acidic protein, several lysosomal markers, and some stres s-response proteins. The ultrastructural appearances of these inclusio ns were distinct, however, one common feature was that they consisted of aggregations of numerous membrane-bound electron-dense bodies. Thus , both inclusions appear to be produced by neoplastic astrocytes and a re possibly related to the lysosomal system. We examined the presence of RGB and EHDs in 138 astrocytic tumors. Both inclusions occurred mos t frequently in pleomorphic xanthoastrocytomas, followed by gangliogli omas and pilocytic astrocytomas. Subependymal giant cell astrocytomas exhibited only RGBs. RGBs and EHDs were not seen in any abundance in g lioblastomas, gliosarcomas, fibrillary astrocytomas, protoplasmic astr ocytomas, or oligo-astrocytomas. Some glioblastomas, however, showed o nly EHDs in small numbers. Several anaplastic astrocytomas were associ ated with a large number of RGBs and/or EHDs, and they revealed only r are mitosis despite marked cellular pleomorphism. Although RGB and EHD s have different morphological features, the presence of these inclusi ons in abundance may represent either a degenerative change, a long-st anding lesion, or an indolent growth of the astrocytic tumors.