Interestingly, H4R expression levels inversely correlated with MI evaluated in melanoma biopsies (Figure 5C, Spearman rho correlation coefficient r: −0.5770, **P = 0.0097) and with PCNA expression (Figure 5B, 5D, Spearman rho correlation coefficient r: −0.7240, ***P = 0.0005), reinforcing the idea of an important relationship between the expression levels of this receptor subtype and the rate of proliferation exclusively in melanomas (Figure 5E–5L). Here, PCNA is linked to melanoma.