Acute promyelocytic leukemia presenting as a paraspinal mass.

Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia (AML) that is characterized by a balanced translocation between chromosomes 15 and 17 [t(15;17)], which results in the fusion of the promyelocytic leukemia (PML) and retinoic acid receptor α (RARA) genes. Historically, APL was a fatal disease because of the high relapse rates with cytotoxic chemotherapy alone and a significant bleeding risk secondary to disseminated intravascular coagulation (DIC). However, APL is now one of the most curable hematological malignancies because of molecularly targeted therapies. With the advent of all-trans retinoic acid (ATRA) containing chemotherapy regimens, rates of complete remission and long-term, disease-free survival have improved dramatically. More recently, regimens incorporating both ATRA and arsenic trioxide (ATO) have allowed a substantial number of patients to be treated with little or no additional cytotoxic chemotherapy.