Tumor-associated macrophages as potential diagnostic and prognostic biomarkers in breast cancer

Breast cancer development largely depends upon the essential contributions from the tumor microenvironment, where several inflammatory cell populations (e.g. macrophages) orchestrate breast cancer development. The majority of tumor-associated macrophages (TAMs) exhibit alternatively activated M2 properties, produce abundant anti-inflammatory factors and facilitate tumor development. Clinical evidences compellingly indicate the association between high TAMs influx and poor prognosis in patients with breast cancers. The pan-macrophage marker CD68 is now generally utilized to identify TAMs in diagnostic biopsy samples, and some other TAM-related biomarkers are also utilized in prognosis prediction, including CD163, vascular endothelial growth factor (VEGF), hypoxia-inducible factors (HIFs), proliferating cellular nuclear antigen (PCNA), ferritin light chain (FTL) and C–C motif chemokine ligand 18 (CCL18). In this review, we highlight the recent progress made in understanding the relationship between TAMs and clinicopathological parameters in human breast cancer and address the potential value of TAMs as diagnostic and prognostic biomarkers.