Single‐Cell Map of Early Lung Adenocarcinoma Uncovers Invasion‐Associated Tertiary Lymphoid Structures

Early lung adenocarcinoma presenting as ground-glass nodules (GGNs) is increasingly detected in clinical practice. However, robust biomarkers reflecting progression from in situ to invasive disease are incompletely defined. Here, we integrated single-cell RNA sequencing, T-cell receptor repertoire profiling, whole-slide immunohistochemistry, multiplex immunohistochemistry, and an orthotopic murine lung adenocarcinoma model to dissect the immune landscape of primary GGNs. We found that these early thoracic lesions harbored abundant infiltrates of innate and adaptive immune cells, but intratumoral T lymphocytes included putative polyclonal bystander clones embedded in an immunosuppressive microenvironment. We further observed a marked stage-dependent increase in T and B cell-rich tertiary lymphoid structures (TLSs), dominated by immature configurations, whereas mature TLSs remained relatively infrequent. In mouse allografts, spontaneously arising TLSs were likewise underdeveloped, and LTαβ or LIGHT overexpression, as well as PD-1 blockade, promoted TLS neogenesis and maturation, accompanied by reduced tumor growth. Collectively, our study delineates the immunologic features associated with pathological invasion, identifies a predominance of structurally immature TLS niches, and provides a rationale for further investigating the therapeutic potential of promoting TLS maturation to intercept early lung adenocarcinoma.