Glial fibrillary acidic protein in ependymomas and other brain tumors. Distribution, diagnostic criteria, and relation to formation of processes.

Glial fibrillary acidic protein (GFAP) was studied in ependymomas by the three-step immunoperoxidase method and compared to results in astrocytomas and normal tissues. An order of reactivity for GFAP is presented. Diagnostic criteria, based on GFAP content, are proposed. In ependymomas GFAP-positive cells give rise to only some of the tumor cells, usually those forming tubules and perivascular arrangements. It is hypothesized that the same GFAP-positive cells may form tubules at their luminal poles and may produce perivascular arrangements at their other poles. The aberrant regulation associated with neoplastic transformation in glia is often, but not always, reflected in increased GFAP content. In both astrocytes and ependymal cells GFAP may have a similar function since in both cells the increase in GFAP appears to be related to the development of fibrillary processes.