S100A9 and neoplasm: Immature myeloid cells, such as myeloid derived suppressor cells (MDSC), have been identified in scRNAseq datasets using S100a9, Ccr2, Cxcr2. While MDSCs have been suggested to promote tumor growth and infiltration through suppressing the anti-tumor immune response, very few were identified in gastric cancer scRNAseq datasets (74).