The significance of programed cell death‐ligand 1 expression in vestibular schwannoma

BACKGROUND: The association between programed cell death‐ligand 1 (PD‐L1) and tumor‐infiltrating lymphocytes (TILs) in vestibular schwannoma (VS) has been investigated in a few studies. These published studies report a difference in the PD‐L1 positivity rate in malignant peripheral nerve sheath tumors. We examined PD‐L1 expression and lymphocyte infiltration in patients with VS who had undergone surgical resection and investigated the association between PD‐L1 expression and clinicopathological features. METHODS: The expression of PD‐L1, CD8, and Ki‐67 in 40 VS tissue specimens was investigated using immunohistochemistry, and a clinical review of the patients was performed. RESULTS: Of the 40 VS samples, 23 (57.5%) were positive for PD‐L1 and 22 (55%) were positive for CD8. No significant differences in age, tumor size, pure‐tone audiometry, speech discrimination, or Ki‐67 expression were observed between patients in the PD‐L1‐positive and PD‐L1‐negative groups. A higher level of CD8‐positive cell infiltration was observed in PD‐L1‐positive tumors than in PD‐L1‐negative tumors. CONCLUSION: We demonstrated that PD‐L1 was expressed in VS tissues. Although no correlation was identified between clinical characteristics and PD‐L1 expression, the association between PD‐L1 and CD8 was confirmed. Thus, additional research on targeting PD‐L1 is necessary to improve immunotherapy for VS in the future.