CD33 and acute lymphoblastic leukemia: T-ALL NOS, and T-cell precursor early acute lymphoblastic leukemia (ETP-ALL) are characterized by an immunophenotype with negative or absent CD1a and CD8 (<5% positive cells), negative or low CD5 (<75% blast cells), and expression of one or more myeloid (CD11b, CD13, CD33, CD117) or stem cell markers (CD34, HLA-DR) [155,165,166].