Role of Tertiary Lymphoid Structures in Autoimmune Diseases and Cancer.

Tertiary lymphoid structures (TLSs) are ectopic, organized immune aggregates forming in non-lymphoid tissues during chronic inflammation. Resembling secondary lymphoid organs (SLOs) architecturally and functionally, TLSs feature specialized stromal networks and compartmentalized immune cell zones. In autoimmunity, TLSs can perpetuate local immune activation, autoantibody production, and tissue damage, correlating with disease severity and progression. In the tumor microenvironment, TLSs are generally associated with enhanced anti-tumor immunity, improved patient survival, and better responses to immunotherapy, although their functional impact can vary across cancer types. This review systematically examines the structural and functional foundations of TLSs and dissects the mechanisms driving their formation in both autoimmune disorders and cancers. We critically evaluate the clinical correlations of TLSs with disease activity, progression, and patient outcomes. Furthermore, we summarize current methodologies for TLS detection and assess their diagnostic and prognostic utility in disease monitoring. Finally, we discuss emerging therapeutic strategies aimed at modulating TLSs formation or function. By synthesizing current knowledge, this review provides crucial insights into TLSs biology within autoimmunity and cancer, highlighting their potential as novel biomarkers and therapeutic targets, thereby advancing our understanding of disease mechanisms and treatment approaches.