DPP4 and skin cancer: However, there is a statistically significant decrease in the percentage of CD26+ overall (white peripheral blood) cells in patients with melanoma in relation to healthy control people (p < 0.00006) as seen in Table 1 and on Figure 2A. In the group of 6 patients with other malignant skin tumors decrease in the percentage of CD26+ overall cells was observed when compared to healthy controls, although this difference had not statistical significance (Wilcoxon rank sum test: W = 61; p = 0.055).