Glial fibrillary acidic protein (GFAP) in oligodendroglial tumors: Gliofibrillary oligodendroglioma and transitional oligoastrocytoma as subtypes of oligodendroglioma

Publisher Website
Google Scholar
Abstract
Summary Immuno-reactivity to glial fibrillary acidic protein (GFAP) is mainly regarded as a sign of astroglial histogenesis and/or differentiation. The presence of astrocytes in oligodendrogliomas is a well known phenomenon; in addition, GFAP-positive neoplastic oligodendrocytes have also been described but have not yet been studied systematically. Using an anti-GFAP serum in the peroxidaseantiperoxidase (PAP) technique, 50 oligodendrogliomas and 16 mixed oligodendrocytomas were investigated; they had been diagnosed by routine histological stains. In half of all oligodendrogliomas, and only in a few (12%) of the mixed oligoastrocytomas, GFAP-positive oligodendrocytes were found in some areas of the classical honey-comb texture with a prominent vascular stroma. The term ‘gliofibrillary oligodendrocyte’ (gfoc) is proposed for these immuno-reactive cells. The existence of a tumour cell combining morphological characteristics of oligodendroglia with GFAP production in its cytoplasm may be considered analogous to transient GFAP expression by myelinforming glia during normal development (Choi and Kim 1984), thus suggesting the return to a foetal behaviour by some neoplastic oligodendrocytes. Three tumours of the present series consisted largely of gfocs and, therefore, may be termed gliofibrillary oligodendrogliomas. In about 32% of all oligodendrogliomas, but only once in the mixed tumour group, a gradual morphological transition from gfocs to gemistocytic astrocytes was observed. This suggested a transitional cell type or transitional oligoastrocytoma as a further subtype of oligodendroglioma, including one example in which minigemistocytes dominated over gfocs (“minigemistocytoma”). These oligodendroglioma subtypes with GFAP-containing cells are different from the mixed oligoastrocytoma which is a tumour of two distinct and non-transitional cell populations.