• Cathal John Hannan, Daniel Lewis, Claire O'Leary, Mueez Waqar, David Brough, Kevin N Couper, Douglas P Dyer, Andy Vail, Calvin Heal, Joshua Macarthur, Christopher Cooper, Charlotte Hammerbeck-Ward, D Gareth Evans, Scott A Rutherford, Simon K Lloyd, Simon Richard Mackenzie Freeman, David John Coope, Andrew T King, and Omar Nathan Pathmanaban.
• Manchester Centre for Clinical Neurosciences, Manchester, UK.
• Neurosurgery. 2023 Mar 1; 92 (3): 581589581-589.

BackgroundThere is evidence that macrophage infiltration in the tumor microenvironment promotes vestibular schwannoma (VS) growth. Efficacy of bevacizumab in NF2-associated VS demonstrates the value of therapies targeting the microvascular tumor microenvironment, and tumor-associated macrophages (TAMs) may represent another druggable target.ObjectiveTo characterize the relationship between growth, TAM infiltration, and circulating monocyte chemokines in a large cohort of patients with VS.MethodsImmunostaining for Iba1 (macrophages), CD31 (endothelium), and fibrinogen (permeability) was performed on 101 growing and 19 static sporadic VS. The concentrations of monocyte-specific chemokines were measured in the plasma of 50 patients with growing VS and 25 patients with static VS.ResultsThe Iba1 + cell count was significantly higher in growing as compared with static VS (592 vs 226/×20 HPF, P =<0.001). Similarly, the CD31 + % surface area was higher in growing VS (2.19% vs 1.32%, P = .01). There was a positive correlation between TAM infiltration and VS growth rate, which persisted after controlling for the effect of tumor volume (aR2 = 0.263, P =<0.001). The plasma concentrations of several monocytic chemokines were higher in patients with growing rather than static VS.ConclusionThere is a strong positive correlation between TAM infiltration and volumetric growth of VS, and this relationship is independent of tumor size. There is a colinear relationship between TAM infiltration and tumor vascularity, implying that inflammation and angiogenesis are interlinked in VS. Chemokines known to induce monocyte chemotaxis are found in higher concentrations in patients with growing VS, suggestive of a potential pathophysiological mechanism.Copyright © Congress of Neurological Surgeons 2022. All rights reserved.

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