BL is a unique entity distinct from other B-cell malignancies. The unsupervised hierarchical clustering, based on the expression of the 9848 most informative genes, clearly separated the different diseases. In particular, eBL, sBL, and HIV-BL were grouped within a unique cluster. The dendrogram was generated with the use of a hierarchical clustering algorithm that was based on the average-linkage method. In the matrix, each column represents a sample and each row represents a gene. The color scale bar shows the relative gene expression changes normalized by the standard deviation (0 is the mean expression level of a given gene).