Tertiary lymphoid structures in neoadjuvant and perioperative cancer immunotherapy: a review and proposed framework for biomarker interpretation and validation.

Tertiary lymphoid structures (TLSs) are associated with immunotherapy response and survival across solid tumors and are increasingly evaluated as tissue biomarkers. Neoadjuvant treatment provides pretreatment biopsies, on-treatment samples, and surgical resections, but these time points answer different clinical questions. Previous reviews have established TLS biology, maturation, and broad associations with response and survival. Here, we organize the evidence by sampling context, measurement object, and intended use. Pretreatment TLSs are candidate baseline stratification markers; within-patient changes describe pharmacodynamic remodeling only when specimens are comparable; and surgical TLSs describe post-treatment response phenotypes or postoperative prognosis according to the outcome time origin. These roles call for distinct validation designs. Immune cells, stromal organizers, and specialized vasculature can reshape TLSs, but parallel structural and tumor changes do not show that treatment benefit depends on TLSs. TLS-specific loss-and-rescue experiments are still needed to test that causal contribution. Clinical translation should therefore start with the decision being made and align the sample, measurement, missingness rules, and validation design to that decision. This framework explains part of the apparent inconsistency across studies and offers a practical path from descriptive associations to clinically interpretable evidence.