Multiplexed single-cell and spatial profiling reveal B cells and tertiary lymphoid structures as prognostic indicators in pleural mesothelioma

BACKGROUND: Pleural mesothelioma (PM) is an orphan disease with poor prognosis. While T cell dynamics in the tumor microenvironment (TME) have been extensively studied, the role of B cells remains poorly characterized. Tumor-infiltrating B cells, particularly when organized into tertiary lymphoid structures (TLS), have been associated with improved outcomes of patients with cancer. METHODS: In this study, high-dimensional flow cytometry (HDCyto) and high-plex imaging were applied to analyze fresh-frozen and formalin-fixed paraffin-embedded (FFPE) PM tumor samples, enabling a comprehensive immune profiling of the TME. RESULTS: We identified 15 distinct immune cell subsets and stratified tumors into three subgroups with significantly different survival outcomes. Longer survival correlated with increased T and B cell infiltration, with B cells and CD4+ T cells forming TLS in specific cases. CONCLUSIONS: These findings underscore the heterogeneity of PM tumors and highlight the critical role of B cells and TLS in shaping anti-tumor immunity and influencing patient prognosis.