The Utility of Phosphohistone H3 in Inter-Observer Variability of Mitotic Count in Meningioma, is There Any Benefit?

OBJECTIVE: One of the most reliable and decisive histologic parameters with negative prognostic impact is tumor proliferation capacity . Quantification of mitosis in H&E stained slides could be problematic and is limited by poor reproducibility and lack of objectivity. This study was designed to evaluate inter-observer variability in mitotic count using Phosphohistone H3(PHH3). METHODS: Totally, 60 specimens with histologic diagnosis of meningioma were selected including 50 grade I, 7 grdae II and 3 grade III tumors. Mitotic figures were counted both in H&E stained sections and slides prepared by immunohistochemistry using Anti-Phosphohistone H3 Anti body by three observers with various level of expertise, independently. RESULTS: Mean mitotic count by PHH3 method was higher than H&E staining for all three observers. Observer 1 and 2 revealed good correlation in mitotic count using H&E method, while observer 3 showed disagreement with both of them. However, all of them had good correlation in mitotic count using PHH3 method (cc=0.956,0.947,0.909). CONCLUSION: Based on our findings, PHH3 revealed good agreement between pathologists with various level of expertise and has the capability for further contribution in meningioma grading classification and specially could be beneficial for less experienced pathologists.