Table 6.

INHAND nomenclature criteria: Benign oligodendroglioma.

Circumscribed lesion with a distinct border, confined to one major area of the central nervous system

Composed of sheets, rows, or nests of small uniform neoplastic cells with round, central, hyperchromatic nuclei and clear to lightly stained cytoplasm (perinuclear halo) with distinct cellular borders

Sheets of neoplastic cells are intersected by fibrovascular stroma.

Pronounced perinuclear halo is common with delayed fixation and results in the essentially artifactual but classically described “honeycomb” or “friedegg” cell pattern.

Prominent microvascular proliferation with atypical capillary endothelial hyperplasia can be extensive, especially at the periphery of the neoplasm.

Necrosis with cystic changes and hemorrhage with hemosiderosis may be present.

Other glial cells, such as astrocytes and transitional forms between oligodendrocytes and astrocytes, may be present in varying numbers.

Abbreviation: INHAND, International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice.