Tumor-infiltrating lymphocytes (TILs) and PD-L1 have emerged as important immune biomarkers in breast cancer, particularly triple negative breast carcinomas (TNBC) and human epidermal growth factor-2 positive (HER-2+) breast carcinomas. These components of the tumor immune microenvironment can be harnessed or targeted with immunotherapy, which represents a significant advancement in the management of TNBC. TILs are a prognostic biomarker in breast cancer, and this recognition has led to reclassification of medullary carcinoma (which were TILs rich by definition) as a pattern of invasive ductal carcinoma (no special type) rather than a distinct histologic type. PD-L1 is a predictive biomarker in TNBC, and two different PD-L1 assays have been approved as companion diagnostics for immune checkpoint inhibition in TNBC. This review will cover the roles of TILs and PD-L1 testing in breast cancer, both of which provide important clinical information to guide patient prognosis and therapy. This is a rapidly evolving and exciting field with significant implications for patient care.
- B7-H1 antigen
- breast carcinoma
- triple negative breast neoplasm
- tumor infiltration
- tumor microenvironment
ASJC Scopus subject areas
- Pathology and Forensic Medicine