Evaluation of Tumor-Infiltrating Leukocytes in Endolymphatic Sac Tumor

Objective: Endolymphatic sac tumors (ELSTs), as rare low-grade neoplasms, are primarily treated with surgery. This study analyzes the characteristics of tumor-infiltrating leukocytes (TILs) in ELSTs and their relationships with clinical features to explore the potential for immunotherapy in ELSTs.

Methods: Clinical data and tumor specimens of 10 ELSTs patients who underwent surgery were retrieved. Immune expression levels of CD3, CD4, CD8, and CD66b were assessed by immunohistochemical staining and expressed as the integral optical density (IOD). Hematoxylin and eosin (HE) staining were performed to define the tumor nest and stroma of ELSTs.

Results: There were no significant differences in the IOD of CD3, CD4, CD8, and CD66b between the tumor nest and stroma or between von Hippel-Lindau (VHL) and non-VHL patients. The IOD of CD3, CD4, CD8, and CD66b appeared relatively higher in patients with endolymphatic hydrops (EH) than those without. Additionally, CD4 expression in the tumor stroma was significantly higher in patients with EH (p = 0.0381).

Conclusion: TILs were present in both ELSTs nest and stroma with significant individual heterogeneity observed among patients. Patients with VHL disease showed a similar immune pattern to those with sporadic ELSTs. Notably, the ELST-related EH may be associated with lymphocytes infiltration. Combined with surgical intervention, immunotherapy may serve as an effective adjuvant therapeutic strategy.

Level of evidence: 4 Laryngoscope, 2025.