P13.04.A CHROMOSOME 1P DELETION AND MCM2 IMMUNOEXPRESSION ARE PROGNOSTICALLY INFORMATIVE IN CHORDOID MENINGIOMAS

Abstract BACKGROUND The chordoid subtype of meningioma is histologically characterized by epithelioid or spindle cells with eosinophilic cytoplasm arranged in cords within a myxoid matrix. Owing to its tendency to recur, it is currently classified as WHO grade 2. Nonetheless, a percentage of chordoid meningiomas exhibit an indolent clinical course that is similar to that of CNS-WHO grade 1 meningiomas. Therefore, features able to stratify chordoid meningiomas according to their recurrence risk could improve postsurgical management. The prognostic significance of chromosome 1p deletion, loss of H3 K27me3 expression, and immunohistochemical expression of MCM2 and ACADL, which serve as indicators for hyperproliferative and hypermetabolic unfavorable molecular groups, has been established in atypical meningiomas. In this study, we aimed to evaluate the prognostic importance of these features, along with the histopathological characteristics, in chordoid meningiomas. MATERIAL AND METHODS Twenty-nine surgically resected intracranial chordoid meningiomas (11 male and 18 female patients; age range: 34-80 years; median age: 54 years) were included in this study. In each case, we analyzed the mitotic index, brain invasion, spontaneous necrosis, immunohistochemical expression of MCM2, ACADL, and H3 K27me3, and chromosome 1p deletion using fluorescent in situ hybridization. Kaplan-Meier curves with log-rank tests were used to analyze the correlations between clinicopathological parameters and recurrence-free (RFS) survival. RESULTS A significantly shorter RFS was recorded in patients older than 65 years (P= 0.0037), in males (P=0.0165), and in meningiomas characterized by a mitotic index ≥ 1.6 mm2, 1p deletion (P= 0.0069), and MCM2 expression (P= 0.0142). H3 K27me3 immunoexpression had no prognostic siognificance in this series. CONCLUSION Chromosome 1p deletion and MCM2 immunoexpression had negative prognostic significance in patients with chordoid meningiomas, similar to that demonstrated in the atypical subtype. These features, along with a high mitotic index, could be used to identify high-risk chordoid meningiomas that could benefit from adjuvant treatment after surgery.