Complex Features of Tumor-Infiltrating Lymphocytes (TILs) and Stromal Response After Neoadjuvant Breast Chemotherapy.

Neoadjuvant chemotherapy (NAC) has become a cornerstone in the management of early-stage breast cancer, offering the dual benefits of downstaging tumors to facilitate surgical resection and providing an in vivo assessment of treatment sensitivity (1-3). The tumor microenvironment (TME), comprising a complex network of stromal cells, immune cells and extracellular matrix, plays a pivotal role in modulating therapeutic response (4-6). Within this ecosystem, tumor-infiltrating lymphocytes (TILs) have emerged as a robust biomarker, while stromal response to therapy - characterized by fibrosis, hyalinization and elastosis - reflects host tissue remodeling and may modulate immune function (1, 7-9) along the stromal response to therapy, characterized by features such as fibrosis, hyalinization and elastosis, reflects the host's tissue remodeling processes and may influence immune cell function and tumor behavior (10-13). This study investigates the dynamic interplay between TILs and stromal features in breast cancer following NAC, aiming to elucidate their combined prognostic and predictive significance (9, 14, 15).