Primary samples from two separate datasets (GSE13159 and GSE26713 including adult and pediatric T-ALL samples, respectively) were identified based on the expression of the oncogenes TLX1, LYL1 and TAL1, and grouped based on unique expression profiles, which correlate with recognized stages of normal thymocyte development; LYL1+ samples resemble thymocytes in the pre-T double negative stage of development, while TLX1+ and TAL1+ samples resemble thymocytes at the early and late cortical stages, respectively [33]. Here, TAL1 is linked to acute lymphoblastic leukemia.