Tumor Infiltrating Lymphocytes in Breast Cancer: Why Is It Useful to Know?

Area of Science:

• Oncology
• Pathology
• Immunology

Background:

• Stromal tumor infiltrating lymphocytes (sTILs) are a readily assessable histopathological biomarker in breast cancer.
• sTILs demonstrate prognostic and predictive value across various breast cancer subtypes, including triple-negative (TNBC), HER2-positive (HER2+), and high-risk luminal breast cancer.

Purpose of the Study:

• To highlight the prognostic and predictive significance of sTILs in breast cancer.
• To emphasize the role of sTILs in predicting response to neoadjuvant chemotherapy and immunotherapy.
• To explore the potential of sTILs in guiding breast cancer treatment strategies.

Main Methods:

• sTILs are evaluated using standard light microscopy on hematoxylin and eosin (H&E)-stained slides.
• Assessment involves quantifying the density of lymphocytes within the tumor stroma.
• Correlation of sTILs scores with clinical outcomes and pathological response.

Main Results:

• Higher sTILs scores on baseline biopsies are associated with increased rates of pathological complete response (pCR).
• Elevated sTILs predict better patient outcomes in response to both chemotherapy and immunotherapy.
• sTILs serve as a robust and reproducible biomarker.

Conclusions:

• sTILs are a powerful predictive biomarker for neoadjuvant therapy response in breast cancer.
• sTILs can inform treatment de-escalation or optimization strategies.
• sTILs aid in selecting patients who may benefit from immunotherapy.