POSTN and melanoma: Because sCD163 is an activation marker for CD163+ tissue macrophages [27], CXCL5 is produced from CD163+ macrophages by POSTN stimulation [14], and POSTN in melanoma is augmented by nonspecific inflammation such as wound healing [15], we hypothesized that the administration of nivolumab in advanced melanoma might increase the expression of POSTN in melanoma tissue, leading stimulated CD163 macrophages to produce sCD163 and CXCL5.