Osteopontin expressions correlate with WHO grades and predict recurrence in meningiomas

Recurrence of meningiomas is a major prognostic issue. Although World Health Organization (WHO) histopathological grading correlates strongly with recurrence, it has some limitations, and predicting the biological behavior of grade I meningiomas is particularly difficult. Osteopontin (OPN) is a protein known to be involved in tumor progression. The purpose of this study is to determine expression of OPN in meningiomas and to investigate its correlation with WHO grades and tumor recurrence. Immunohistochemical (IHC) evaluation of expression of OPN was performed by two different methods to ensure reliability. OPN IHC and Allred scores were calculated on the basis of intensity and extent of staining. Both scores were in agreement and correlated significantly with meningioma grade and Ki-67 index. OPN scores were also significantly correlated with recurrence of WHO grade I meningiomas. Cut-off values for OPN IHC and OPN Allred scores between non-recurrent and recurrent grade I meningiomas were calculated as 70 and 5.5 respectively. We concluded that OPN is a valuable marker for grading meningiomas and for predicting the recurrence in WHO grade I tumors.