ULTRASTRUCTURAL CHARACTERIZATION OF OLIGODENDROGLIAL-LIKE CELLS IN CENTRAL-NERVOUS-SYSTEM TUMORS

Cells with uniform, small-round nucleus and clear cytoplasm (oligodend roglial-like cell, OLC) are commonly observed in central nervous syste m (CNS) neoplasm of glial and neuronal lineage, such as oligodendrogli oma, clear-cell ependymoma, and central neurocytoma. Immunohistochemis try does not always contribute to the characterization of OLC because of (1) loss of antigen expression; (2) lack of specific markers for ol igodendrogliomas; and (3) occasional coexpression of neuronal and glia l antigens. An ultrastructural analysis associated with an immunohisto chemical study of 20 cases of CNS tumors largely constituted by OLCs h as been performed. Neurocytomas (12 cases), medullocytomas (2 cases), cerebral neuroblastoma (1 case), and ganglioglioma (1 case) showed OLC s with ultrastructural features of neuronal differentiation (neuritic processes, dense-core granules, synaptic structures). Oligodendrogliom a (3 cases) OLCs were characterized by mitochondrial-rich cytoplasm, a nd ependymoma (1 case) OLCs showed microrosettes and scattered cilia. The electron microscopic analysis can provide a more precise diagnosis of these OLC-containing tumors despite their uniform morphological ap pearance.