Unsupervised clustering of T-ALL samples based on `ectopic' genes. The 469 probe sets differentially expressed between oncogenic groups (Figure 4A) were filtered for ectopic expression with reference to expression in normal thymic subpopulations and bone marrow, resulting in a working list of 23 ectopically expressed genes. Genes known to be involved in development are boxed. The main T-ALL oncogenic subgroups and annotations are indicated as in other figures.