Characterization of Tumor Immune Microenvironment in Meningiomas: Correlation of Tumor-infiltrating Lymphocyte Aggregates With Tumor Grade.

Abstract

Background/aim: Malignant meningiomas are aggressive intracranial tumors with high recurrence rates and limited treatment options. The tumor immune microenvironment (TIME) plays a pivotal role in the tumor progression and treatment response. However, its role in meningioma remains largely unknown. This study aimed to analyze tumor-infiltrating lymphocytes (TILs) within the meningioma TIME and investigate their correlation with clinical parameters.

Patients and methods: Using tumor specimens from patients diagnosed with meningioma (grade 1, 12 cases; grade 2, 10 cases), the densities of CD4+ T-cells, CD8+ T-cells, CD20+ B-cells, and tissue-resident memory T-cells were quantified using multicolor immunohistochemistry and the QuPath software. The results were analyzed along with clinical parameters, including tumor grades.

Results: The density of individual TIL subsets did not correlate with the tumor grades or patients' postoperative neurological function. TIL aggregates were observed in grade 2 meningiomas; clusters of abundant B-cells with a few follicular helper T-cells were observed in one case, indicating the presence of immature tertiary lymphoid structures. A positive correlation was observed between the densities of CD4+ and CD8+ T-cells in grade 2 meningiomas but not in grade 1.

Conclusion: The TIME in meningiomas exhibits distinct immune profiles by tumor grade, characterized by the presence of TIL aggregates and coordinated CD4+ and CD8+ T-cell infiltration in higher-grade tumors. These findings may provide insights into the immune landscape of meningiomas and support the development of immunotherapeutic strategies targeting the TIME.