Principal component analysis to find subgroups within the malignant samples. A set of 16 miRNAs could be used to separate the malignant samples according to Gleason scores (GS) with the exception of three samples: one GS 6 sample placed in the GS 7 group, one GS 7 sample placed in the GS 6 group, and one GS 7 sample placed in the GS 9 group. In the figure, one GS 7 sample is hidden behind another GS 7 sample. The strings between samples correspond to their nearest neighbors. Blue: GS 6, green: GS 7, yellow: GS 9, white: GS 10.