Acute promyelocytic leukemia (APML, APL) is the M3 subtype of acute myelogenous leukemia (AML), a cancer of the white blood cells.[1] In APL, there is an abnormal accumulation of immature granulocytes called promyelocytes. The disease is characterized by a chromosomal translocation involving the retinoic acid receptor alpha (RARα or RARA) gene and is distinguished from other forms of AML by its responsiveness to all-trans retinoic acid (ATRA; also known as tretinoin) therapy. Acute promyelocytic leukemia was first characterized in 1957[2][3] by French and Norwegian physicians as a hyperacute fatal illness.[1] Currently it is one of the most treatable forms of leukemia with a 12-year progression-free survival rate that is estimated to be approximately 70%.[1][4]