[MBP and GFAP immunohistochemistry of oligodendrogliomas with relationship to myelin-forming glia in cell differentiation].

The histologic feature of oligodendroglioma is constituted by the monotonously arranged sheets of tumor cells intersected with delicate vascular stroma. The shape of the tumor cells is usually uniform and occasionally rather pleomorphic. In order to clarify biological characteristics of the tumor cells at level of cell differentiation, immunohistochemical stains for myelin basic protein (MBP) and glial fibrillary acidic protein (GFAP) with PAP method were performed on 13 oligodendrogliomas obtained by surgical removal. The cells stained positive with MBP immunostain were encountered in 5 tumors and their incidence was ranging from 1% to more than 30% of all tumor cells. The MBP-positive cells were characterized by having a large clear nucleus with a prominent nucleolus and relatively abundant cytoplasm, that seemed to mimic myelin-forming glia appearing in normal developing brain. The cells with poor cytoplasm or surrounded by a perinuclear halo were MBP-negative, and the pleomorphic cells in majority of anaplastic oligodendrogliomas were also negative. On the other hand, with GFAP stain the positive cells were observed in 8 tumors. It is still controversial to interpret the occurrence of GFAP-positive cells in oligodendrogliomas. In this study the GFAP-positive cells were morphologically identical to the MBP-positive cells, so that both MBP and GFAP are supposed to exist in the same tumor cells. It is assumed that some of oligodendroglioma cells which showed such immunostainabilities could possess an intrinsic character to express a phenotype of myelin-forming glia. Possibly, MBP substance is applicable as one of immunohistochemical markers for oligodendroglioma cells to indicate a certain cell differentiation.