Comparison of bromodeoxyuridine uptake and MIB 1 immunoreactivity in medulloblastomas determined with single and double immunohistochemical staining methods.

We examined the growth potential of 17 medulloblastomas by single and double immunohistochemical staining with bromodeoxyuridine (BUdR) and MIB 1, a monoclonal antibody for Ki-67 protein, in serial sections of ethanol-fixed, paraffin-embedded tissues; we also assessed the heterogeneity of the immunoreactivity in the tumors. In the most active areas, the BUdR labeling index (LI) was 6.8 to 26.9% (HCl hydrolysis) and 7.5 to 28.8% (microwave heating), and the MIB 1 proliferating cell index (PCl) was 14.9 to 56.5%. Linear regression analysis showed that the BUdR LI correlated with the MIB 1 PCI (p < 0.001). The ratio of MIB 1-positive to BUdR-positive cells was 2.2 +/- 0.4 by both single and double staining. BUdR-positive nuclei were heterogeneously distributed in all cases, especially in areas with scattered foci of necrosis. Three tumors had areas with many MIB 1-positive but few BUdR-positive nuclei; these areas were associated with recent tumor necrosis. However, in most of the tumors, the densities of BUdR-positive and MIB 1-positive cells changed concomitantly from area to area. These changes were clearly shown by double immunostaining. Thus, transcapillary passage of BUdR does not appear to be impeded in most medulloblastomas. This study suggests that MIB 1 immunostaining provides essentially the same data as BUdR labeling for assessing the proliferative potential of medulloblastomas.