ABSTRACT
Objective: To investigate the differences of immune microenvironment between stage T1N3 and stage T3N0 breast cancer patients and explore the relationship between M1 macrophage infiltration and lymph node metastasis in breast cancer. Methods: Clinical information and RNA-sequencing (RNA-Seq) expression data of stage T1N3 (n=9) and stage T3N0 (n=11) breast cancer patients were extracted from Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) databases. Using CIBERSORT, the proportions of 22 types of immune cells were calculated, and then the differences of immune cell infiltration between stage T1N3 and T3N0 patients were compared. From 2011 to 2022, pathologic specimens were collected from breast cancer patients who underwent curative resection at the Cancer Hospital, Chinese Academy of Medical Sciences, including 77 at stage T1N3 and 58 at stage T3N0.The METABRIC database analysis results were verified by examining the density of M1 macrophages in tissues using dual-staining immunohistochemistry. Results: METABRIC data analysis showed M1 macrophage was the highest proportion, 15.85% in stage T1N3 breast cancer; M2 macrophage was the highest proportion, 13.07% in stage T3N0 breast cancer.M1 macrophage proportions were statistically different between patients with stage T1N3 and stage T3N0 (P=0.010). The dual-staining immunohistochemistry analysis of breast cancer tissues showed M1 macrophage density (median) of 62.0 and 38.0 cells/mm(2) for stage T1N3 and T3N0, respectively. The difference was statistically significant (P=0.002). Conclusion: The density of M1 macrophages is notably higher in stage T1N3 patients and is associated with lymph node metastasis.