S100A8 and neoplasm: In the published literature, S100A8 and S100A9 are reported as predominantly expressed within tumors by immune cells, and their expression can stimulate the recruitment of myeloid22, 23 and myeloid-derived suppressor cells24 to promote pre-metastatic niche formation, tumor growth and metastasis.25 S100A8 and S100A9 are also expressed by tumor cells,26 and although there have been many studies detailing the functions of stromal-derived S100A8 and S100A9, little is known about the effects of tumor-derived S100A8 and S100A9.