Prognostic Significance of B7-H3 Expression and CD163+ Tumor-Associated Macrophage Infiltration in Mesothelioma

Mesothelioma is a rare, aggressive malignancy with poor prognosis. B7-H3 (CD276), an immune checkpoint molecule, and CD163-positive tumor-associated macrophages (TAMs) contribute to tumor progression and immune evasion. This study evaluated the prognostic impact of B7-H3 expression and CD163-positive TAM infiltration. This single-center retrospective study included 94 patients diagnosed with malignant mesothelioma between 2011 and 2024. B7-H3 expression was assessed using the H-score method and dichotomized at the cohort median. CD163-positive TAM density was quantified in hotspot high-power fields. Overall survival (OS) was analyzed using Kaplan–Meier, log-rank, and multivariable Cox regression analyses. Median OS was 10.15 months (IQR: 4.88–19.66). High B7-H3 expression was associated with shorter OS, whereas high CD163-positive TAM density was associated with longer OS. In multivariable analysis, B7-H3 expression, CD163 expression, tumor localization, recurrence status, and treatment status were independently associated with overall survival. Combined biomarker analysis showed the worst OS in the CD163-low/B7-H3-high group and the best OS in the CD163-high/B7-H3-low group. High B7-H3 expression was independently associated with shorter overall survival, whereas high CD163-positive TAM infiltration was associated with longer overall survival in this cohort. The combined B7-H3/CD163 profile may identify distinct prognostic subgroups and highlights the tumor immune microenvironment.