Definition:

Acute promyelocytic leukemia (APL) is the most malignant form of acute myeloid leukemia (AML) with a severe bleeding tendency and a fatal course of only weeks. Morphologically, it is identified as AML-M3 by the FAB classification. APL is characterized by a balanced reciprocal translocation between chromosomes 15 and 17, which results in the fusion between the promyelocytic leukemia (PML) gene and retinoic acid receptor alpha (RARA). The majority of APL patients present with the classic PML-RARA translocation. However, approximately 5% of patients with APL have a non- characteristic translocation. Other chimeric proteins have been observed including PLZF-RARA, NUMA1-RARA, and so on.