Early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) is a small subtype of T-cell acute lymphoblastic leukemia with a typical immune-phenotype: lack of T-lineage cell surface markers CD1a and CD8 expression, weak or absent CD5 expression, at least one of the myeloid or hematopoietic stem cell markers. The gene discussed is CD5; the disease is T-cell acute lymphoblastic leukemia.