Tertiary Lymphoid Structures in Brain Metastases of Lung Cancer: Prognostic Significance and Correlation With Clinical Outcomes

Abstract

Background/aim: The prognosis of patients with brain metastases (BMs) originating from lung cancer remains poor, despite advancements in treatment strategies. The role of tertiary lymphoid structures (TLSs) within the tumor immune microenvironment of BMs has not been extensively explored.

Patients and methods: This study utilized patient-derived clinical samples from 17 patients with histologically confirmed BMs of lung cancer, undergoing surgical resection. Immunohistochemistry was employed to analyze the presence and characteristics of TLS and tumor-infiltrating lymphocytes (TILs) within BM tissues, correlating these with clinical outcomes.

Results: TLSs, albeit in their immature form, were identified within BM tissues, distinguishing them from their mature counterparts in primary lung cancer tissues. A significant correlation between TLS density (but not TIL density) and improved postoperative survival was observed, underscoring the potential of TLS density as an independent prognostic marker. Furthermore, TLS density did not correlate with the Graded Prognostic Assessment (GPA) index, suggesting its unique prognostic value beyond conventional predictors.

Conclusion: Our findings reveal the presence of TLSs in lung cancer-derived BMs and highlight their prognostic significance, independent of the GPA index. The identification of TLS within the unique central nervous system tumor microenvironment offers new insights into the immune landscape of BMs and suggests potential avenues for immunotherapeutic interventions targeting these structures to improve patient outcomes.

Keywords: Tertiary lymphoid structures; brain metastases; lung cancer; prognostic biomarkers; tumor immune microenvironment (TIME).