ETP-ALL/LBL is immunophenotypically defined by weak or absent expression of T cell markers (CD1a, CD5, and CD8) and positive expression of at least one hematopoietic stem cell (HSC) and/or myeloid markers (CD13, CD33, CD34, CD117, and HLA-DR). The gene discussed is CD1A; the disease is acute lymphoblastic leukemia.