The majority of T-ALL cases may be subclassified into subtypes according to the aberrant expression and dysregulated pathways of transcription factors and oncogenes induced by leukemia-initiating alterations involving basic helix–loop–helix (bHLH) factors (TAL1, TAL2, LYL1), homeobox genes (TLX1 (HOX11), TLX3 (HOX11L2), NKX2-1, NKX2-5, HOXA), LMO1, LMO2, MYB, BCL11B and SPI1 (Figure 2) [5,135,136]. The gene discussed is TAL1; the disease is acute lymphoblastic leukemia.