Abstract
Background : We report two cases demonstrating typical oligodendroglioma, focusing on the characteristic cytological features, and discuss the importance to OLIG2 expression and 1p19q deletions.
Case : Case 1 was 60-year-old female and case 2 was 60-year-old male, respectively. They complained of subjective symptoms, such as vertigo and convulsions, and a mass was found in the right parietal lobe of brain by magnetic resonance imaging. Squash smears showed a loose cluster of round tumor cells with scant cytoplasm in both cases 1 and 2. Although there were aggregates of capillary vessels, there were no mitotic figures or necrosis. The nuclei of tumor cells were irregular with small inconspicuous nucleoli and fine chromatin patterns. Histologically, tumors appeared monotonous with clear cytoplasm and capillary vessels. There were no mitotic figures, necrosis or endothelial proliferation in the tumor. On immunohistochemistry, the tumor expressed OLIG2 protein and showed a low Ki-67 labeling index. Furthermore, 1p19q deletions were identified in both cases 1 and 2 by fluorescence in situ hybridization.
Conclusion : Diagnosis of oligodendroglioma requires differentiation from other brain tumors demonstrating small round cells. Characteristic cytological findings of oligodendroglioma are round tumor cells with irregular nuclei and capillary vessels. Furthermore, detecting overexpression of OLIG2 and 1p19q deletions also contributes to the differential diagnosis from other brain tumors.
