Brain Invasion in Meningioma—A Prognostic Potential Worth Exploring

Abstract

Most meningiomas are slow growing tumors arising from the arachnoid cap cells and can be cured by surgical resection or radiation therapy in selected cases. However, recurrent and aggressive cases are also quite common and challenging to treat due to no established treatment alternatives. Assessment of the risk of recurrence is therefore of utmost importance and several prognostic clinical and molecular markers have been established. Additionally, the identification of invasive growth of meningioma cells into CNS tissue was demonstrated to lead to a higher risk of recurrence and was therefore integrated into the WHO classification of CNS tumors. However, the evidence for its prognostic impact has been questioned in subsequent studies and its exclusion from the next WHO classification proposed. We were recently able to show the prognostic impact of CNS invasion in a large comprehensive retrospective meningioma cohort including other established prognostic factors. In this review we discuss the growing experiences that have been gained on this matter, with a focus on the currently nonuniform histopathological assessment, imaging characteristics and intraoperative sampling as well as the overall outlook on the future role of this potential prognostic factor.

Mib1 Expression Is Increased in Meningiomas with Histopathological Evidence of Cns Invasion

“…This supports the decision expressed in the new WHO classification for CNS tumors, which still incorporates CNS invasion as a stand-alone criterion for atypia [2]. Understandably, the role of infiltrative growth in brain parenchyma is still controversial, especially due to non-standardized sampling and histopathological grading as recently expressed [16,11]. Our data provide a contribution to this topic, but more robust studies are needed to further our understanding of the mechanism of CNS invasion.…”

“…First of all, the histopathological characteristics used to determine infiltrative growth are not clearly defined [10,11] and possibly vary between departments and neurooncological centers. Additionally, intraoperative tumor sampling is non-standardized and especially areas of interest may not always be amenable to appropriate sampling [16]. We recently compared the prognostic potential of histopathological and intraoperative detection of infiltrative growth in 1517 meningiomas.…”

Increased proliferation is associated with CNS invasion in meningiomas

“…First of all, the histopathological characteristics used to determine infiltrative growth are not clearly defined [ 10 , 11 ] and possibly vary between departments and neurooncological centers. Additionally, intraoperative tumor sampling is non-standardized and especially areas of interest may not always be amenable to appropriate sampling [ 16 ]. We recently compared the prognostic potential of histopathological and intraoperative detection of infiltrative growth in 1517 meningiomas.…”

“…This supports the decision expressed in the new WHO classification for CNS tumors of 2021, which still incorporates CNS invasion as a stand-alone criterion for atypia [ 2 ]. Understandably, the role of infiltrative growth in brain parenchyma is still controversial, especially due to non-standardized sampling and histopathological grading as recently expressed [ 11 , 16 ]. Our data provide a contribution to this topic, but more robust studies are needed to further our understanding of the mechanism of CNS invasion.…”

Combining FORGE Score and Histopathological Diagnostic Criteria of Atypical Meningioma Enables Risk Stratification of Tumor Progression

“…The results of the ROC curves and the subsequent analysis of PFS demonstrate that the AT-FORGE score is a sufficient add-on to the conventional FORGE scoring system in atypical meningioma regarding the prediction of PFS. The predictive value of brain invasion in meningioma has been highly debated due to contradictory results regarding overall survival and progression-free survival [31][32][33]. Nevertheless, evidence of mitotic count as the second major diagnostic criteria in the prediction of the clinical endpoint "local progression-free survival" is stronger compared to brain invasion [34,35].…”