L1CAM and neoplasm: Intriguingly, mature TLSs may express L1 Cell Adhesion Molecule (L1CAM), a feature not observed in immature TLSs, and the employment of L1CAM as a marker for mature TLSs achieves a high level of observer agreement.424 Further investigations have elucidated a negative correlation between the presence of TLSs and patient tumor progression, particularly noting a significant extension in progression-free survival when CD23+ GCs are contained within TLSs.