A Proposal for a Modified Evaluation System of Tumor‐Infiltrating Lymphocytes Using HE‐Stained Sections in Breast Cancer

Tumor-infiltrating lymphocyte (TIL) scoring in tumor specimens has gained increasing attention in determining patients who are likely to benefit from immunotherapies. However, the histological evaluation methods of TILs in breast cancer remain limited. This study aimed to assess four components of lymphocytic reaction and overall lymphocytic score (L-score) used in colorectal cancer, investigate its association with clinicopathological factors, and examine the effect of TILs on postoperative mortality using 231 invasive breast cancers without neoadjuvant chemotherapy. Besides L-score, increasing modified L-score lacking peritumoral lymphocytic reaction was significantly associated with aggressive breast cancer phenotypes, including larger invasive size, higher tumor stage, higher Ki-67 labeling index, triple negative and HER2-enriched subtypes, and higher Nottingham histological grade. Importantly, modified L-score status but not L-score or TIL-Working Group (WG) score status was positively correlated with the disease-specific survival rate of the overall patients as well as the patients with luminal type or histological Grade III breast cancers. These results indicated that the modified L-score is a favorable method to comprehensively assess lymphocytic reaction to predict prognosis among patients with breast cancer, even compared with the currently used TIL-WG method, which may possess their potential integration into clinical practice.