S-100 protein in human glial tumours. Qualitative and quantitative studies

The authors studied a total of 48 human glial tumours for S-100 protein, an extremely acidic, protein specific to the nervous system, by immunohistochemistry and by micro-complement fixation assay in order to evaluate S-100 protein as an index for malignancy of glial tumours. All of 48 glial tumours analyzed in the present study demonstrated variable amounts of S-100 protein which might serve as a biochemical cell marker for glial tumours. The mean value of S-100 protein content in 3 ependymomas is higher than those of 19 low-grade (grades I, II) astrocytomas and 26 high-grade (grades III, IV) astrocytomas, being lowest in the latter. A statistically significant (P less than 0.001) difference in S-100 protein levels between low- and high-grade astrocytomas is observed, but not for ependymoma. At present, however, no correlation can be found between S-100 protein content of a tumor and the patient's survival time. Immunoperoxidase staining for S-100 protein in high-grade astrocytomas is generally weak in intensity and heterogeneous throughout the section, whereas that in low-grade astrocytomas and ependymomas is relatively strong and homogeneous, indicating that high-grade astrocytomas consist of a more heterogeneous population of tumour cells in terms of S-100 protein. These results show that the investigation of S-100 protein in a glial tumor is valuable to a certain extent in assessing the degree of differentiation or malignancy of the tumour.