Dendrograms showing tissue classification by hierarchical clustering analysis with the 56 genes. The dendrograms shown were generated with standard two-way hierarchical clustering analysis of GenePattern using the expression values of the (A) 56 signature genes or (B) randomly selected 56 genes extracted from the 24 tissues under the three GEO datasets. The associated heatmaps are displayed in Additional file 1: Fig. S1 and Fig. S2, respectively.