S100A9 and neoplasm: In a variety of tumors, S100A9 forms a heterodimer with S100A8, S100A8/A9, which interferes with the tumor microenvironment and metabolism, promotes tumorigenesis, progression and metastasis, and serves as a tumor diagnostic and prognostic marker as well as a potential therapeutic target (Wang et al., 2018; Ye et al., 2019; Chung et al., 2023).