Prognostic significance of the mitotic index using the mitosis marker anti-phosphohistone H3 in meningiomas

Abstract

Mitotic activity is one of the most reliable prognostic factors in meningiomas. The identification of mitotic figures (MFs) and the areas of highest mitotic activity in H&E-stained slides is a tedious and subjective task. Therefore, we compared the results from immunostaining for the mitosis-specific antibody anti-phosphohistone H3 (PHH3 mitotic index [MI]) with standard MF counts (H&E MI) and the Ki-67 labeling index (LI). The relationship between these proliferation indices and prognosis was investigated in a retrospective series of 265 meningiomas. The PHH3 staining method yielded greater sensitivity in the detection of MFs and facilitated MF counting. Mitotic thresholds of H&E MI of 4 or more per 10 high-power fields (HPF) and PHH3 MI of 6 or more per 10 HPF were found as the most appropriate prognostic cutoff values for the prediction of recurrence-free survival. All 3 proliferation indices were univariately associated with recurrences and deaths. In contrast with the Ki-67 LI, H&E MI and PHH3 MI also remained as independent predictors in the multivariate Cox hazards modeling (P = .0007 and P = .0004, respectively).