An immunohistological study of 66 ependymomas.

Sixty-six ependymomas were examined immunohistologically to determine their distribution of glial fibrillary acidic proteins, S-100 protein and vimentin. The neoplasms were subdivided into four groups: (1) ependymomas from the cauda equina, predominantly of the myxopapillary type; (2) benign ependymomas; (3) malignant ependymomas; and (4) ependymoblastomas. Marked differences in antigen reactivity were observed between each group. The intensity of the reaction with the three antibodies was strongest in malignant ependymomas. Ependymomas from the cauda equina showed a patchy distribution of positivity for the three antigens in cells surrounding blood vessels but there was no staining of collagenous septa or the myxoid areas. In ependymoblastomas, the cells of the rosettes were negative for glial fibrillary acidic protein, but there was focal positivity for vimentin and S-100. Other areas showed tumour cells containing moderate amounts of vimentin and small amounts of S-100, and a few bands of filaments positive for glial fibrillary acidic protein. The cytogenetic and biological implications of these findings are discussed.