Macrophage and Lymphocyte Infiltration Is Associated with Volumetric Tumor Size but Not with Volumetric Growth in the Tübingen Schwannoma Cohort

Abstract

Most patients with vestibular schwannomas can be cured with microsurgical resection, or tumor growth can be stabilized by radiotherapy in certain cases. Recurrence is rare but usually difficult to treat. Treatment alternatives to local therapies are not established. There is growing evidence of the role of inflammatory processes in schwannomas, which may be exploitable by targeted innovative therapies. To further define the impact of inflammation with tumor growth in vestibular schwannoma, we performed immunohistochemical analyses of CD3, CD8, CD68 and CD163 to assess lymphocyte and macrophage infiltration in 923 tumor tissue samples of surgically resected vestibular schwannomas. An inflammatory score was compared with tumor size and volumetric growth. We observed a significantly larger preoperative tumor size with increased expression rates of CD3, CD8, CD68 and CD163 (p < 0.0001, p < 0.0001, p = 0.0015 and p < 0.0001, respectively), but no differences in percentual volumetric tumor growth. When all four markers were combined as an inflammatory score, tumors with high inflammatory infiltration showed slower percentual growth in a multivariate analysis, including MIB1 expression (p = 0.0249). We conclude that inflammatory cell infiltration increases with larger tumor size but is associated with slower percentual volumetric tumor growth.