Correlation of glial fibrillary acidic protein (GFAP) with grading of the neuroglial tumours

Abstract

Objective: To determine the distribution of glial fibrillary acidic protein (GFAP) in human neuroglial tumours and its correlation with histologic grading.

Design: Analytical.

Place and duration of study: Postgraduate Medical Institute, Lahore, on the cases from 1999 to 2001.

Materials and methods: Fifty formalin fixed paraffin-embedded tissue blocks were obtained. Two sections from each block were taken. One was stained with heamatoxylin-eosin stain while second for GFAP that is the unlabelled antibody immunoperoxidase (peroxidase - antiperoxidase PAP) method was used. The non-neoplastic brain tissue was used as positive control, while cases reported medulloblastoma tumour was used as negative control. We applied a scoring scale 0 to 3+, to evaluate its correlation with the grade of tumour.

Results: In positive control only the cell process and perikaryons of fibrous astrocytes was stained. The 35 cases of various grade astrocytoma showed a varying intensity of GFAP staining. Similarly, 3 cases of glioblastoma multiforme, 2 cases of sub-ependymal giant cell astrocytoma, 2 cases of pleomorphic xanthoastrocytoma, 2 out of 4 cases of ependymoma and the case of oligoastrocytoma showed a positive reaction. The stain was more intense over processes than in perikaryons, with the exception of gemistocytic astrocytomas and the giant cells in glioblastoma multiforme, which showed an equally intense stain over perikaryons and processes. Comparison of the histological grade with GFAP score was significantly higher in high grade tumour when compared with tumour of grade I (p<0.001). In astrocytic neoplasms the number of GFAP positive cells and the intensity of the stain were directly proportional to the degree of malignancy. All the 3 cases of oligodendroglioma showed a negative reaction to GFAP. Only astrocytic component was positive which are poorly visualize by H&E stain.

Conclusion: The GFAP score shows significant relation with the present WHO grading system of glial tumours. GFA protein is specific for glial cells and it is useful to diagnose those glial tumours which are difficult to be identified by heamatoxylin-eosin stain or due to rare or unusual site.