The TLX1 (T CellLeukemia Homeobox 1) gene, located at 10q24.31, encodes a nuclear transcription factor and belongs to the NK-linked or NK-like (NKL) subfamily of homology box genes. The encoded protein is required for normal spleen development in embryogenesis and is also involved in neuronal cell regulation. Considered an oncogene, translocation expression following chromosomal translocations has been associated with certain T-cell acute lymphoblastic leukemias (T-ALL).The incidence of TLX1 gene rearrangements in T-cell acute lymphoblastic leukemias (T-ALL) is approximately 20% to 30%, and the occurrence of patients with a positive TLX1 gene break is suggestive of a favorable prognosis.