Tumor-infiltrating lymphocytes and PD-L1 in breast cancer (and, what happened to medullary carcinoma?)

Research output: Contribution to journalReview articlepeer-review


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.

Original languageEnglish (US)
JournalDiagnostic Histopathology
StateAccepted/In press - 2021


  • B7-H1 antigen
  • breast carcinoma
  • immunotherapy
  • lymphocytes
  • triple negative breast neoplasm
  • tumor infiltration
  • tumor microenvironment

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Histology


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