Fig. 3

Correlation between PD-L1 and COX-2 expression in primary (a) and metastatic lymph node (b) of melanoma tumors. COX-2 expression, graded as a semi-quantitative variable, was correlated with PD-L1 expression scored as negative (0+), light positive (1+) and positive (2+) when the PD-L1 score in an entire lesion was 0, 1–5, and >5% respectively. Difference in the expression of COX-2 in according to PD-L1 groups was analyzed using the Kruskal–Wallis rank test. On each box, the central mark is the median, the edges of the box are the 25th and 75th percentiles, the whiskers extend to the most extreme data points not considered outliers, and outliers are plotted individually. P value is indicated