It was shown that several S100 family members, including S100A2, S100A4, S100A6, S100A7, S100A8, S100A9, and S100A11 are up- or downregulated in breast cancer compared with healthy tissue, suggesting that S100 proteins play a crucial role in tumour development and progression [81,82] and as predictive biomarkers [83,84,85,86,87,88]. Here, S100A9 is linked to breast cancer.