Hierarchical clustering of 69 tumor samples with available gene expression data. Clustering was based on 364 genes from the intrinsic gene list published by Sørlie and colleagues  that matched our cDNA clones. Colored boxes indicate classification of each tumor into subtypes/subgroups. Filled or open boxes indicate the percentage of cells in each tumor positive for the CD44+/CD24- and CD44-/CD24+ phenotypes as determined by immunohistochemistry. SR, steroid receptor. Hu classification, Hu and colleagues .