Infiltrating pattern and prognostic value of tertiary lymphoid structures in resected non-functional pancreatic neuroendocrine tumors

BackgroundTertiary lymphoid structures (TLS) are associated with favorable survival and play a critical role in most solid tumors. However, investigations of TLS are lacking in patients with grade 1 or grade 2 (G1/G2) non-functional pancreatic neuroendocrine tumors (NF-PanNETs). This study aimed to investigate the presence, cellular composition, association with tumor-infiltrating immune cells, and prognostic value of TLS in G1/G2 NF-PanNETs.MethodsTumor tissues from a 182-patient Fudan cohort and a 125-patient external validation set were assessed by H&E staining, immunohistochemistry, and/or multispectral fluorescent immunohistochemistry.ResultsTLS were identified in more than one-third of patients with G1/G2 NF-PanNETs and were located peritumorally, either just outside the tumor tissue or in the stromal area. TLS were mainly composed of B-cell follicles with germinal centers and T-cell zones with dendritic cells. Kaplan-Meier analyses showed that the presence of TLS correlated with both longer recurrence-free survival (RFS, p