C Boxplots showing the distributions of the normalized rank-sums of the up-regulated (left panel) and down-regulated (right panel) genes in the identified signature. Down-regulated genes in Primary-B melanomas better discriminate the two groups of primary melanoma samples (p=5.9e-15, Wilcoxon rank-sum test). Median, minimum, maximum, 25th, 75th whiskers of ranksum distribution are shown. 