A study of astrocytes in retinoblastomas using the immunoperoxidase technique and antibodies to glial fibrillary acidic protein

We identified astrocytes in 12 of 14 randomly selected formalin-fixed Paraplast-embedded retinoblastomas, using the avidin-biotin-peroxidase complex of the immunoperoxidase techniques and antibodies to purified glial fibrillary acidic protein. In two of these eyes, both of which had extensive choroidal invasion by retinoblastoma, we found no tumor cells containing glial fibrillary acidic protein. Astrocytes were observed in metastases within the neurologic tissue of the central nervous system in two cases, but were rarely noted in metastatic foci within the subarachnoid space, and were not found in distant metastases to other sites. These findings suggested that although some astrocytes may become incorporated into retinoblastomas from the retina as the neoplastic cells proliferate and the tumor grows, others proliferate in response to the tumor. Although we found foci of cells containing glial fibrillary acidic protein in some retinoblastomas, convincing evidence of glial differentiation from tumor cells was not observed in any of the retinoblastomas we studied.