MNGO-06. CLINICAL COURSE OF GRADE II MENINGIOMAS INDICATE POSSIBILITY OF OVER DIAGNOSIS

Abstract

Up to 30 % of meningiomas are diagnosed as WHO grade II based on the current WHO classification criteria. However, report on clinical prognosis of those tumors in the modern era with the technical advancement is scarce. We reviewed the clinical course and pathological findings of recent grade II meningioma cases. Adult intracranial meningioma cases from 2009 to 2014 were included in this study. All cases were histologically reviewed again and were classified as grade I or II meningiomas according to the new WHO 2016 criteria. There were 52 female and 12 male patients with ages ranging from 25 to 87 yeas (median 58). Thirty-seven were diagnosed grade I, and 27 as grade II. Seven cases were excluded due to poor sample status for histological diagnosis. Grade II tumors were divided into two subgroups; group IIa (n = 10) with increased mitosis in a localized area, and group IIb (n = 17) either with increased mitosis in several areas, satisfying soft criteria, or brain invasion. The age of grade IIb (median 69) was higher than that of grade I and IIa (median; 57 and 50, respectively). Female to male ratio in grade IIb was relatively high (29.4%). MIB-1 labeling index was also higher in grade IIb (median 10.3) than grade I and IIa (median; 3.0 and 2.1, respectively). Clinically, recurrences were observed in 6 cases; 5 in grade IIb and 1 in grade I. There were no recurrence in grade IIa cases. This study indicates that some meningioma cases diagnosed as grade II according to the WHO 2016 may have better clinical behavior than predicted. Further studies with larger cases may delineate those tumors with better prognosis and lead to refinement of the criteria.