Unsupervised hierarchical clustering of normal and neoplastic B-cell samples. The dendrogram (top part) is based on the expression pattern of the 2000 probe sets (corresponding to 1535 named genes) varying the most across the dataset (and thus being the most informative); their expression pattern is depicted in the clustered heat map and color bar below (bottom part). Very similar results were obtained when using a higher or lower number of highly variant probe sets or when the clustering was restricted to the primary tumors and corresponding most variant probe sets (ie, excluding the influence of normal B cells and HL lines; not shown). In addition, the coclustering of cHL with NLPHL and of PMBL with the non-HLs was consistently observed even when restricting the analysis only to cHL, NLPHL, and PMBL or only to cHL, NLPHL, PMBL, and DLBCL (not shown). The HL line cluster is formed, from left to right, by DEV (nLPHL), HDLM2 (T-cell cHL), KMH2, L1236, and L428 (B-cell cHL). N indicates naive B cells; M, memory B cells; and PC, plasma cells.