Lymph node preservation as an immunotherapeutic catalyst.

Lymph nodes are vital immunological organs, yet nodal surgery-including sentinel lymph node biopsy and completion lymph node dissection-is routinely performed in many solid tumors. Importantly, nodal surgery remains clinically valuable in selected settings, particularly for pathological staging and treatment decision-making, and in some contexts for regional disease control. We address a central paradox in surgical oncology: while lymph node dissection aims to control regional metastasis, emerging immunology suggests that intact tumor-draining regional lymph nodes can support antitumor immunity during immune checkpoint blockade. Although the immunological principles discussed may be relevant across a range of solid tumors, the most direct evidence to date comes from immunotherapy-treated settings-particularly tumor types with established checkpoint inhibitor activity-and from studies of regional, non-metastatic (tumor-draining) lymph nodes; whether these observations extend to immunotherapy-refractory tumors or metastatic nodes remains to be determined. Emerging evidence from preclinical models and correlative human studies suggests that tumor-infiltrating immune responses can be seeded from tumor-draining regional lymph nodes, supported by intratumoral tertiary lymphoid structures (ectopic lymphoid aggregates within tumors) and tumor-associated high endothelial venules (specialized venules that facilitate lymphocyte entry). With advances in imaging and drug-delivery platforms, even metastatic lymph nodes may also be addressed via non-surgical strategies. We propose the "Lymph Node Catalyst" hypothesis as an integrative, testable framework: preserved nodal-vascular circuits act as immunological reservoirs that may enhance responses to immunotherapy. This perspective reframes lymph nodes from solely metastatic waystations to context-dependent immune hubs in the immunotherapy era.