PML and acute promyelocytic leukemia: Acute promyelocytic leukemia (APL) is characterized by an aberrant chromosomal translocation that fuses a portion of the promyelocytic leukemia (PML) gene with the retinoic acid receptor α (RARα) gene [1], and subsequent expression of the PML-RARα oncoprotein causes a block at the promyelocytic differentiation stage.