The Significance of Immunohistochemical Expression of Merlin, Ki-67, and p53 in Meningiomas

Meningiomas are one of the most common CNS tumors whose appearance is closely linked to NF2 gene product merlin. Tumor markers Ki-67 and p53 play established role in tumor progression which should be analyzed in close association with merlin expression. The aim of this study was to investigate the immunohistochemical expression of merlin in meningiomas, correlation with Ki-67 and p53, and to determine the association of these results with histologic grade and subtype. The histologic sections of 170 patients with totally resected meningiomas, between January 2000 and December 2010, were classified according to WHO, immunohistochemically stained for Ki-67, p53, and merlin, and analyzed using light microscope. Ki-67 median was 5.6 times higher in group of patients with negative merlin than in those with positive merlin (P=0.05). Statistically significant correlation of merlin with p53 was found (P<0.001). Merlin expression between 2 combined groups (meningothelial/secretory and fibroblastic/transitional) was statistically significant (P=0.002). By comparing merlin expression and p53 levels, statistically significant difference was found (P=0.017). In the group with positive merlin and negative p53 as well as positive merlin and low p53, meningothelial/secretory subtypes of meningiomas were more common. In combination of negative merlin and negative p53 as well as negative merlin and high p53, there were more meningiomas of fibroblastic/transitional subtype. There was no statistically significant correlation between merlin and tumor grade (P=0.420). There is undeniable influence of merlin on the development and the proliferative ability of meningioma subtypes. Significant role of p53 pathway was confirmed.