The impact of brain invasion criteria on the incidence and distribution of WHO grade 1, 2, and 3 meningiomas

Abstract

Background In 2016, brain invasion was added as a standalone diagnostic criterion for Grade 2 meningiomas in the WHO Classification of Brain Tumors. The aim of this study was to compare the incidence and distribution of meningiomas, and agreement, between the 2007 and 2016 WHO criteria. Methods All cases of intracranial meningiomas diagnosed between 2007 and 2020 at a tertiary care academic hospital were identified. The incidence of each meningioma grade in the WHO 2007 and WHO 2016 cohorts were compared. Additionally, each case in the 2007 cohort was re-graded according to the WHO 2016 criteria to determine the intra-class correlation (ICC) between criteria. Results Of 814 cases, 532 (65.4%) were in the 2007 WHO cohort and 282 (34.6%) were in the 2016 WHO cohort. There were no differences in the distribution of meningioma grades between cohorts (p=0.11). Incidence rates were: 75.0% v. 75.2% for Grade 1, 22.7% v. 24.5% for Grade 2, and 2.3% v. 0.4% for Grade 3, for the 2007 and 2016 cohorts, respectively. Upon re-grading, 21 cases (3.9%) were changed. ICC between original and revised grade was 0.92 (95% CIs: 0.91-0.93). Amongst Grade 2 meningiomas with brain invasion, 75.8% had three or more atypical histologic features or an elevated mitotic index. Conclusions Including brain invasion as a standalone diagnostic criterion for Grade 2 meningiomas had minimal impact on the incidence of specific meningioma grade tumors. There is strong agreement between the 2007 and 2016 WHO criteria, likely due to cosegregation of grade elevating features.

Differences in intraoperative sampling during meningioma surgery regarding CNS invasion – Results of a survey on behalf of the EANS skull base section

“…With the advent of CNS invasion as a stand-alone criterion for atypia in the WHO classification since 2016, an unusual increase in cases with histopathological CNS invasion was observed, presumably based on a tendency of some pathologists to assign a higher grade when in doubt ( Perry, 2021 ). On the other hand, a larger retrospective study of 814 meningiomas showed only a slight non-significant increase of WHO 2 meningiomas after the inclusion of CNS invasion in the WHO classification ( Rebchuk et al., 2022 ). Therefore, a varying adherence to the criteria of CNS invasion proclaimed by the recent WHO classification can be suspected, although they have been defined quite clearly, with pial breach and protrusion of meningioma tissue into GFAP-positive tissue as proof of invasive growth.…”

Multiparameter MRI-based radiomics nomogram for preoperative prediction of brain invasion in atypical meningioma:a multicentre study

“…The reason for this is that the new, revised criteria include BI as an independent, histological criterion for diagnosing AM. Formerly WHO grade 1 meningioma patients were included as having AM once the new BI-based criterion was applied to them, resulting in an increase of 1–10% in the incidence of AM [ 23 , 34 ], as well as an increase in the proportion of BI in AM. In terms of clinical risk factors for BI in AM, our study found that patient sex, age, tumor location, and V Tumor were not involved, consistent with the findings of several studies [ 8 , 29 ].…”

ADC histogram parameters differentiating atypical from transitional meningiomas: correlation with Ki-67 proliferation index

“…Meningiomas are the most common primary central nervous system tumors in adults (1,2), accounting for 39.0% of all intracranial tumors (3). They are divided into three grades and 15 subtypes according to the 2021 World Health Organization (WHO) Central Nervous System (CNS) tumor classification (3).…”