The use of the monoclonal antibody Ki-67 in determination of the growth fraction in pediatric brain tumors.

Using the monoclonal antibody Ki-67, proliferating cells were demonstrated immunohistochemically in 16 tumors of the nervous system in children, and these findings compared with those in 44 adult tumors. The antibody, which reacts with a nuclear protein expressed during the G1, S, G2, and M phases of the cell cycle, was demonstrated in frozen (13 cases) or smear (3 cases) sections using the peroxidase-antiperoxidase method. The percentage of stained tumor cells in children was in general agreement with the histological grade, ranging from 0.2% in a schwannoma to 12.4% in a juvenile type of glioblastoma. In a medulloblastoma, the fraction of labeled nuclei was 10.2%. In malignant gliomas of children, the percentage of stained cells did not differ from that in adult tumors. However, some cases demonstrated an unusually higher number of positive cells associated with higher cellularity than did adult tumors; this is in agreement with the content of small immature tumor cells in many pediatric tumors. The use of Ki-67 staining could become an important additional criterion for predicting the biologic behavior of nervous system neoplasms in children.