title: Immune infiltrates in the breast cancer microenvironment: detection, characterization and clinical implication.
abstract: Although unlike melanoma, breast cancer is not generally viewed as a highly immunogenic cancer, recent studies have described a rich tumor immune microenvironment in a subset of breast cancers. These immune infiltrates, comprised cells from the innate and adaptive immune response, can be detected and characterized in biopsy specimens and have prognostic value. Tumor-infiltrating lymphocytes (TILs) represent the majority of mononuclear immune infiltrates in the breast tumor microenvironment and can be easily identified in formalin-fixed paraffin-embedded tissues after standard hematoxylin and eosin staining. High levels of TILs are most common in HER2+ and basal-like subtypes where they are associated with good prognosis and with response to certain therapies such as the anti-HER2 antibody trastuzumab. International collaborative efforts are underway to standardize the assessment of TILs so as to facilitate their implementation as a breast cancer biomarker. Using immunohistochemistry to further characterize TILs, recent reports describe the presence of important lymphocyte populations including CD8+ cytotoxic, FOXP3+ regulatory, and CD4+ helper and follicular T cells which have overlapping associations with prognosis and response to therapies. Moreover, recently identified immune checkpoint markers (PD-1, PD-L1) are present in some breast cancers, implying some cases might be especially amenable to immune checkpoint inhibitor treatment strategies which are being evaluated in a number of active clinical trials.
authors.affiliation: Pathology and Laboratory Medicine, Anatomical Pathology JPN 1401, University of British Columbia, 855 W. 12th Avenue, Vancouver, BC, V5Z 1M9, Canada.
authors.forename: Samantha
authors.initials: S
authors.lastname: Burugu
authors.affiliation: Pathology and Laboratory Medicine, Anatomical Pathology JPN 1401, University of British Columbia, 855 W. 12th Avenue, Vancouver, BC, V5Z 1M9, Canada.
authors.forename: Karama
authors.initials: K
authors.lastname: Asleh-Aburaya
authors.affiliation: Pathology and Laboratory Medicine, Anatomical Pathology JPN 1401, University of British Columbia, 855 W. 12th Avenue, Vancouver, BC, V5Z 1M9, Canada. torsten@mail.ubc.ca.
authors.forename: Torsten O
authors.initials: TO
authors.lastname: Nielsen
mesh_terms: D014408:Biomarkers, Tumor / Q000276:immunology; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000276:immunology* / Q000473:pathology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D060908:CTLA-4 Antigen / Q000276:immunology; D005260:Female; D006801:Humans; D007113:Immunity, Innate; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology* / Q000473:pathology; D008264:Macrophages / Q000276:immunology / Q000473:pathology; D061026:Programmed Cell Death 1 Receptor; D050378:T-Lymphocytes, Regulatory / Q000276:immunology; D059016:Tumor Microenvironment / Q000276:immunology*
chemical_list: D014408:Biomarkers, Tumor; D060908:CTLA-4 Antigen; C105992:PDCD1 protein, human; D061026:Programmed Cell Death 1 Receptor
keywords: Breast cancer; Immune microenvironment; Prediction; Prognosis; Tumor-infiltrating lymphocytes