Impact of tumor infiltrating lymphocytes and lymphoid follicle formation on patient survival following surgery for lung squamous cell carcinoma.

Background: Tumor infiltrating lymphocytes (TILs) are known to correlate with the prognosis of patients affected by a variety of cancer types. We evaluated TILs in patients who underwent surgery for lung squamous cell carcinoma (SCC).

Methods: Specimens obtained from patients during resection of lung SCC were examined for TIL density, lymphoid follicle formation, PD-L1 expression, and the appearance of regulatory T cells (Tregs).

Results: We enrolled 72 patients who underwent surgery for SCC (TIL grades 0, 1, and 2: 29, 18, and 25, respectively). Lymphoid follicles were observed in 13 (18.1%) patients and 8 were positive for Tregs, which were always observed in association with lymphoid follicles (P < 0.001). Multivariate analysis revealed that lymphoid follicle formation, the appearance of Tregs, pathological stage, and pleural invasion were independent prognostic factors related to overall survival, whereas TIL density and PD-L1 expression were not.

Conclusion: SCC patients with lymphoid follicle formation accompanied by Tregs show poor survival following lung resection surgery.