Chordoid glioma of the third ventricle: Report of a case with cytologic features and utility during intraoperative consultation

Background: Chordoid glioma is a rare, low grade neoplasm with a unique chordoid appearance as well as distinct clinicopathologic and immunohistochemical features. Its cytologic features have not been described. Case: A 42-year-old woman with recent-onset amnesia and confusion underwent magnetic resonance imaging, which revealed a 5-cm mass lesion arising in the third ventricle. Intraoperative squash smears showed cellular sheets as well as nests and strands of epithelioid tumor cells with bland nuclei and polygonal to elongated cytoplasm in a mucinous background. Binucleation was commonly seen. The tumor was intimately admixed with a benign lymphoplasmacytic infiltrate and scattered Russell bodies. Histologically, the tumor cells were arranged in a syncytium with prominent lymphoplasmacytic infiltrates and scattered small foci of necrosis in a mucinous matrix. The foremost differential diagnosis was chordoid meningioma. Immunohistochemically, the tumor cells were positive for glial fibrillary acid protein (GFAP), vimentin, epithelial membrane antigen, CD34, neuron-specific enolase and CK-7 and negative for synaptophysin, S-100 protein, neurofilament, and estrogen and progesterone receptors. Conclusion: Intraoperative smear cytology in this case of chordoid glioma revealed distinctive cytologic features, reflecting the unique histologic pattern. Cytologic features, such as binucleation, absence of intranuclear pseudoinclusions and GFAP immunoreactivity, are particularly helpful in differentiating chordoid glioma from chordoid meningioma.