S100A9 and neoplasm: In previous studies, S100A9-specific (=S100A8/S100A9) in vivo imaging for the detection of local monocytic activity in the TME as a surrogate for tumor aggressiveness and development has been established [4], while beforehand evaluation of S100A8/S100A9 and MDSC in humans and mice was focused on ex vivo analyzes from peripheral blood and lymphatic organs.