Clustering analyses of normal and tumour samples based on microRNA expression. (a) Samples were clustered using cube-rooted data and correlation-based distance (as described in Additional File 9). Two large subgroups and one small outgroup resulted, with separations 1N:1T, 29N:1T and 0N:28T, respectively. The small outgroup consisted of tumour and normal samples from patient G428. The remaining samples were partitioned among the two larger subgroups, one of which consisted of the other 29 normal samples and one tumour sample, and the other consisted of the remaining 28 tumour samples. (b) Samples were clustered using the distance metric defined in Section 4.1 of Berninger et al. . Again, an outgroup and two major subgroups resulted, with separations 0N:2T, 25N:2T and 5N:26T, respectively. For both panels, 'N' indicates a normal sample and 'T' indicates a tumour sample. Note: the duplicates of G699N and G761T are clustered near each other in both methods.