Oligodendrogliomas (OL) are neuroepithelial tumors characterized by the presence of uniformly round nuclei with a clear cytoplasm around it. These features can also be seen in central neurocytomas, DNTs and clear cell ependymomas. Immunohistochemstry with glial and neuronal markers may be helpful in diferential diagnosis. The aim of this study was to determine the glial and neuronal differentiation in 42 specimes of otherwise typical OL using immunohistochemical techniques. Ten cases showed anaplastic characteristics. Thirty-three samples (78.5%) were positive to GFAP with few cells stained in ten cases and many positive cells in six. Twelve cases (28.5%) were focally positive to NSE and/or synaptophysin showing neuronal differentiation. Thirty-four cases (80.9%) expressed S-100. In conclusion, glial proteins may be present focally in OL due to presence of mature reactive astrocytes or transitional forms between astrocytes and oligodendrocytes. Focal areas of neuronal differentiation can also be found in typical OL. The widespread staining with neuronal marker suggests central neurocytoma, but this diagnosis should not be done with small amount of tissue.
oligodendrogliomas; neuronal markers; imunohistochemstry
