Subependymal giant cell astrocytoma. Significance and possible cytogenetic implications of an immunohistochemical study.

Twenty-two cases of subependymal giant cell astrocytoma (SGCA), five of which associated with tuberous sclerosis, were reviewed by conventional neurohistological stains and by peroxidase-antiperoxidase (PAP) immunohistochemistry for glial fibrillary acidic (GFA) protein, the 68 Kd neurofilament subunit (68 Kd-NF), and neuron-specific enolase (NSE). Neurohistological stains confirmed the presence of PTAH-positive fibrils and the absence of Nissl bodies and of neurites originating from the tumor cells. GFA protein-positive cells were present in all tumors not associated with tuberous sclerosis. However, the number of positive cells in each tumor was highly variable. GFA protein-positive cells were rare in the two SGCA accompanying tuberous sclerosis and absent in the remaining three. Neurohistological stains showed no differences between GFA protein-positive and negative cells. 68 Kd-NF-positive cells were found in six tumors. In one tumor, associated with tuberous sclerosis, it was present in the large ganglion-like cells only. NSE-positive cells were found in 13 of 18 tumors examined, including four of the five SGCA associated with tuberous sclerosis. The significance of NSE-positivity in central neuroepithelial neoplasms in respect of their possible neuronal origin remains open. This study suggests that the SGCA, especially those associated with tuberous sclerosis, include cells that are apparently unable to express GFA protein. Some of the tumor cells express the 68 Kd-NF, but this expression falls short of the complete expression of neuronal differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)