PML and acute promyelocytic leukemia: Acute promyelocytic leukemia (APL) is a unique subset of acute myeloid leukemia (AML) whose pathogenesis revolves around a translocation involving the retinoic acid receptor (RAR) locus on chromosome 17, most commonly the t (15; 17) (q22; q11), giving rise to the PML–RARα fusion gene that encodes an oncoprotein.