MIXED GLIOMAS

Although the preceding gliomas are often portrayed as pure entities, many contain other cell types or hybrid cells with partial expressions of more than one type. Thus the oligodendroglioma can contain cells with astrocytic characteristics, or an ependymoma or cerebellar astrocytoma may include dozens of "fried eggs." The term mixed glioma is applied when a second cell type is present in quantity, but when present in limited numbers, a second cell type can be noted but not included in the diagnosis. At present, the significance of these mixed lesions is not known. Presumably, the application of markers for specific glia will continue to define the incidence and character of mixed gliomas, and careful correlative clinical studies will establish their prognostic significance.