Because the main population of TAMs in skin cancer is CD163+ M2 macrophages, and soluble cluster of differentiation 163 (sCD163) is a TAM marker that appears in the serum as a result of proteolytic shedding (15), we hypothesized that serum sCD163 may offer a predictive marker for the efficacy of nivolumab in the early stage of disease. Here, CD163 is linked to skin cancer.