134 Clinicopathological and Molecular Characteristics of Pediatric Versus Adult Meningiomas

Abstract

Abstract INTRODUCTION Molecular and clinical characteristics of pediatric meningiomas are poorly defined. Aim of this study was to analyze clinical features, morphological spectrum and molecular profile of adult and pediatric meningiomas METHODS Sixty four adult and forty pediatric meningiomas from January 2002 to June 2015 were assessed for 1p36 14q32 and 22q deletion by FISH and progesterone receptor (PR), p53 along with MIB-1 LI using immunohistochemistry (IHC). Pediaric cases were also assessed for AKT and SMO mutations by sequencing, and expression of GAB1, stathmin, progesterone receptor (PR) by IHC. RESULTS >In the paediatric group, there were 36 sporadic and 4 NF2 associated meningiomas. Amongst sporadic meningiomas, majority (72.2%) of cases harboured 22q deletion. Difference in frequency of combined 1p/14q deletion in Grade I versus Grade II/III tumors was not significant (13.7% vs 28.5%, P = 0.57). PR immunoreactivity was seen in 65.5% of Grade I and 14.2% of Grade II/III tumors (P = 0.03). Majority (97.2%) of meningiomas were immunonegative for p53. GAB and stathmin co-expression was observed in 58.3% of cases. AKT and SMO mutations were seen in none. Frequency of 1p/14q codeletion was higher in skull base tumours as compared to non skull base meningiomas (23% vs 11.1%, p 0.37). All NF2 meningiomas harboured 22q deletion and showed GAB and stathmin co- expression while none showed 1p/14q loss. In adults, deletion of both 1p and 14q were seen in grade II and grade III convexity meningiomas, in 28.5% and 30% of cases, respectively, while it was absent in grade I convexity tumors. Hormone profile of adult cases was similar to pediatric group. CONCLUSION Pediatric meningiomas share phenotypic and genotypic characteristics with adult counterparts, but GAB and stathmin co-expression in majority of cases and no significant difference in frequency of 1p/14q co-deletion between low and high grade meningiomas indicate inherently aggressive nature. SMO and AKT mutations are distinctly absent.