Glial fibrillary acidic protein in giant cell tumors of brain and other gliomas

Summary

The giant cell tumor of brain (glioblastoma/sarcoma) has been considered a glioma by some and a sarcoma by others. This study shows that glial fibrillary acidic protein (GFAP), a specific “marker” for astrocytes, is present in the tumor cells, thus indicating that the cell of origin is the astrocyte and that the tumor should be called a giant cell glioblastoma. GFAP is present in the smaller cells of this tumor and in larger mononucleated cells, but little if any is detectable in multinucleated giant cells.

In a different kind of tumor, the giant cell astrocytoma assonciated with tuberosclerosis, GFAP is restricted in most cells to a narrow peripheral zone.

Immunocytochemical localization of GFAP is superior to “special stains” to differentiate giant cell glioblastomas from true sarcomas and giant cell bone tumors, since the latter are both negative for GFAP.

Comparison of GFAP in all tumors of astrocyte origin shows that the cells that appear to contain the most GFAP include low grade well differentiated stellate cells, elongated “piloid” cells, and gemistocytic astrocytoma cells. Highly malignant undifferentiated cells, with less well developed processes, are less densely positive.

Although there is in general an inverse relationship between GFAP content and degree of tumor malignancy, a more complex relationship exists with respect to individual cells; more GFAP is present in well differentiated cells with well-developed processes and filaments than in undifferentiated cells and large multinucleated cells. It is suggested that the pleomorphism of more malignant cells may relate to their relatively low GFAP content and perhaps to the disassembly of their glial filaments.