Fig 2. Histologic findings of tumor area A (A and B), tumor area B (C and D), and tumor area C (E and F). (H&E, x200 [A, C, and E], MIB-1 immunostaining, hematoxylin counterstaining, x200 [B, D, and F].) A, Tumor area A is moderately cellular and composed of cells with rounded, homogeneous nuclei and a swollen, clear cytoplasm (honeycomb appearance), consistent with low-grade oligodendroglioma. B, Tumor area A has MIB-1 positive cells and an MIB-1 labeling index of 1.8%. C, Tumor area B shows increased cellularity, marked cytological atypia, and high percentage of mitotic activity, consistent with high-grade (anaplastic) oligodendroglioma. D, Tumor area B shows frequent MIB-1 positive cells and an MIB-1 labeling index of 7.6%. E, Tumor area C is moderately cellular and composed of cells with rounded, homogeneous nuclei with calcification, consistent with low-grade oligodendroglioma. F, Tumor area C shows MIB-1 positive cells and an MIB-1 labeling index of 2.2%.