Samples from 274 patients with DLBCL were assigned to one of 3 classes by hierarchical clustering according to the expression of 100 genes. Amplification of the c-rel locus and bcl-2 translocations were limited to the germinal center B-cell–like group. Kaplan-Meier estimates of overall survival after chemotherapy for 240 previously untreated patients are shown, demonstrating differences in clinical outcome between the gene expression subgroups. Reprinted from Rosenwald et al³¹  with permission.