What is the designation for Acute Promyelocytic Leukemia?

Acute Promyelocytic Leukemia (APL) is classified as AML M3 in the World Health Organization classification of acute myeloid leukemias. This specific designation is significant because APL is characterized by specific genetic abnormalities, primarily the translocation t(15;17), which leads to the fusion of the promyelocytic leukemia gene (PML) and the retinoic acid receptor alpha gene (RARA). This fusion plays a critical role in the pathogenesis of the disease, affecting the differentiation of myeloid cells and leading to the accumulation of promyelocytes in the bone marrow and peripheral blood.

The identification of APL as AML M3 is crucial since it has distinct clinical manifestations and a specific therapeutic approach, including the use of all-trans retinoic acid (ATRA) and arsenic trioxide, which have transformed the prognosis for patients with this subtype of acute myeloid leukemia. Thus, recognizing the correct designation is vital for diagnosis, treatment decisions, and understanding the biology of the disease.