Meningiomas (MGM) often exhibit clinically aggressive progression, although being primarily benign. Immunotherapy could be an alternative treatment, but knowledge regarding meningioma immunobiology remains limited. This study delved into less explored subtypes, such as B-cells, NK-cells, and granulocytes, to analyze their associations with disease progression and cell-cell relations.

A cohort comprising 100 primary MGM cases was used, including all WHO grades (°1, °2, and °3), and DNA-methylation classes (MC; benign, intermediate, and malignant). To quantify infiltration of T cells, B cells, NK cells, neutrophils, and eosinophils, tumor tissue cryo-sections were obtained from the institutional biobank. Immunofluorescence stainings were performed on tumor cryo-sections and digitized as high-resolution multiple image alignments for semi-automated cell counting. The infiltration rates were then correlated with clinical data, including clinical grading, age, sex, progression-free survival (PFS) and overall survival.

Each subtype´s median cell infiltration varied, with T cells (0.64%) having the highest, followed by neutrophils (0.079%), B cells (0.003%), NK cells (0.006%), and eosinophils (0.0018%). B cell infiltration correlated with increasing T cells, as did eosinophils with neutrophils. WHO°1 cases exhibited higher NK cell and eosinophil infiltration compared to other WHO-grades. High NK cell infiltration was characteristic of the benign MC. Neutrophils and NK cells infiltrated more in the younger sub-population (<61yo). Overall, patients with higher PFS tended to have higher infiltration of T cells, NK cells, and eosinophils, but lower B cells and neutrophils. Aggregates of T cells and B cells were found on 10% of cases, which also showed high infiltration rates of all cell types and higher PFS.

This study provides infiltration rates of rarer immune cell subtypes and their variation with clinical grading, age, and sex, as well as their relevance for MGM progression.