Ultrarapid Evaluation of Meningioma Malignancy by Intraoperative Flow Cytometry

Abstract

The prognosis for World Health Organization (WHO) grade II/III meningiomas is worse than for WHO grade I meningiomas. Histopathologic grade should ideally be identified during tumor resection, but current methods are time-consuming and have doubtful reliance. The aim of this study was to evaluate intraoperative flow cytometry (iFC) as a method for providing ultrarapid evaluation of meningioma malignancy. A total of 117 meningiomas were analyzed with iFC during surgery. For each, the malignancy index (MI) was calculated as the number of cells with a greater than normal DNA content as a proportion of the total number of cells. Each specimen was investigated histopathologically and was diagnostically graded according to the 2016 WHO grading system. MI results were compared with WHO grades of the meningiomas. The automatic measurement of iFC took approximately 9 minutes on average. The difference in MI between grade I and grade II/III meningiomas was statistically significant (P < 0.001). Receiver operating characteristic analysis provided an optimal cutoff MI value of 8.0% for discrimination between grade I and grade II/III groups, with 64.7% sensitivity and 85.0% specificity for grade II/III meningiomas. Our method of calculating MI with iFC appears to be technically feasible and reliable for ultrarapid evaluation of meningioma malignancy. MI with iFC could potentially enable determination of an optimal treatment strategy during surgery, such as extent of resection of the tumor and management of invaded normal brain or nerves.