RARA and acute promyelocytic leukemia: APL is a unique disease entity in AML, characterized by a large proportion of patient carriers t(15;17)(q24;q21) involving the promyelocytic leukemia (PML) gene at chromosome band 15q24 and the retinoic acid receptor alpha (RARA) gene at 17q21, generating an aberrant PML-RARA fusion gene [140,146].