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Review
. 2021 Aug 23;13(16):4233.
doi: 10.3390/cancers13164233.

Tumor Microenvironment in Breast Cancer-Updates on Therapeutic Implications and Pathologic Assessment

Joshua J Li  1 , Julia Y Tsang  1 , Gary M Tse  1
Affiliations
Review

Tumor Microenvironment in Breast Cancer-Updates on Therapeutic Implications and Pathologic Assessment

Joshua J Li et al. Cancers (Basel). .

Abstract

The tumor microenvironment (TME) in breast cancer comprises local factors, cancer cells, immune cells and stromal cells of the local and distant tissues. The interaction between cancer cells and their microenvironment plays important roles in tumor proliferation, propagation and response to therapies. There is increasing research in exploring and manipulating the non-cancerous components of the TME for breast cancer treatment. As the TME is now increasingly recognized as a treatment target, its pathologic assessment has become a critical component of breast cancer management. The latest WHO classification of tumors of the breast listed stromal response pattern/fibrotic focus as a prognostic factor and includes recommendations on the assessment of tumor infiltrating lymphocytes and PD-1/PD-L1 expression, with therapeutic implications. This review dissects the TME of breast cancer, describes pathologic assessment relevant for prognostication and treatment decision, and details therapeutic options that interacts with and/or exploits the TME in breast cancer.

Keywords: breast cancer; fibrotic focus; stromal response; tumor infiltrating lymphocytes; tumor microenvironment.

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Conflict of interest statement

The authors declare that there is no conflict of interest regarding the publication of this paper.

Figures

Figure 1
Figure 1
Effects of (a) Radiotherapy and (b) Chemotherapy on the Breast Cancer Tumor Microenvironment.
Figure 1
Figure 1
Effects of (a) Radiotherapy and (b) Chemotherapy on the Breast Cancer Tumor Microenvironment.
Figure 2
Figure 2
Tumor infiltrating lymphocytes on H&E sections. (a) Breast cancer with dense stromal infiltrating lymphocytes, H&E, 200× magnification; (b) Breast cancer with sparse lymphocytic infiltrates, H&E, 200×.
Figure 3
Figure 3
Fibrotic Foci on H&E Sections. (a) H&E, 20×; (b) H&E, 100×.
Figure 4
Figure 4
Immunohistochemistry for immune cells in the tumor microenvironment. (a) CD8 stain highlights cytotoxic T-cells among lymphocytes, CD8, 200×; (b) CD68 highlights tumor associated macrophages which are difficult to identify by H&E, CD68, 200×.
Figure 5
Figure 5
PD-L1 Immunohistochemistry. (a) Example of negative PD-L1 expression in tumor and immune cells, Ventana SP142, 200×; (b) Positive PD-L1 staining in tumor and immune cells, Ventana SP142, 200×; (c) Positive staining in immune cells only, Ventana SP142, 400×.
Figure 6
Figure 6
CD31 stain for assessment of microvessel density, CD31, 200×.
See this image and copyright information in PMC

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