MIB-1 counting methods in meningiomas and agreement among pathologists

OBJECTIVE: To evaluate the correlation of MIB-1 labeling index (LI) obtained by 2 counting methods with histologic grade and investigate interobserver variability between these methods. STUDY DESIGN: A total of 65 meningiomas were analyzed for proliferation with 2 counting methods by 2 pathologists using MIB-1 antibody. In the first method, the most densely staining areas were counted (HL method). In the second method, randomly selected areas were counted (RS method). RESULTS: MIB-1 values correlated well with histologic grade in both methods. As expected, the tumors with recurrence had significantly higher LIs than the nonrecurrent tumors in each method. However, there was a statistically significant difference in the mean MIB-1 values of between the HL and RS methods. When MIB-1 LI was compared between 2 pathologists, perfect agreement in the HL method and substantial agreement in the RS method were achieved. CONCLUSION: Our results showed that values of MIB LIs differ with different counting methods. Nonetheless, both methods showed good correlation with World Health Organization grades. Therefore standardization of 1 counting method is of great importance for determining a reliable and specific cutoff value in assessing the risk of recurrence in meningiomas.