Immunocytochemistry of cerebellar astrocytomas: with a special note on Rosenthal fibres.

Two astrocytic immunocytochemical markers, glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS), were demonstrated in cerebellar astrocytomas. The staining pattern for both antigens was similar, but GFAP demonstrated astrocytic processes better, while GS staining was stronger in poorly fibrillated cells. The various astrocytic forms, bipolar, stellate, bi- and multi-nucleate cells, displayed different immunostaining. Rosenthal fibres also showed a varying pattern of reaction: larger fibres were entirely negative or had a narrow peripheral ring of dense reaction product, but occasional smaller fibres were positive. The varying proportion of filamentous and amorphous material within Rosenthal fibres could be responsible for this finding. The pale granular bodies possessed a GFAP-positive limiting membrane and GS-positive contents, suggestive of their astrocytic origin. Immunohistochemistry of GFAP and GS has contributed to the knowledge of cellular differentiation and secondary changes in cerebellar astrocytomas.