With respect to differences of the mRNA expression level of 34 immune checkpoints in melanoma, the results displayed that the expression levels of most immune checkpoints, such as ADORA2A, BTLA, CD200, CTLA4, CEACAM1, and PDCD1, were significantly higher in the low-risk group compared to the high-risk group (Figure 5(g)). This evidence concerns the gene PDCD1 and melanoma.