Medical Laboratory Scientist (MLS) ASCP Practice Exam

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What type of leukemia is known as Acute Promyelocytic Leukemia?

  1. FAB M1

  2. FAB M2

  3. FAB M3

  4. FAB M5

The correct answer is: FAB M3

Acute Promyelocytic Leukemia (APL) is classified as FAB M3 in the French-American-British (FAB) classification system of acute myeloid leukemias. This specific type of leukemia is characterized by the presence of promyelocytes with heavy granulation and often is associated with a genetic translocation involving the promyelocytic leukemia (PML) gene on chromosome 15 and the retinoic acid receptor-alpha (RARA) gene on chromosome 17, which results in the formation of the PML-RARA fusion protein. This fusion protein interferes with normal myeloid differentiation and leads to the accumulation of promyelocytes, contributing to the distinct clinical and cytological features of APL. Patients with APL often present with bleeding diathesis due to coagulopathy and can benefit from all-trans retinoic acid (ATRA) therapy, which targets the effects of the PML-RARA fusion protein. Other classifications within the FAB M system correspond to different types of acute myeloid leukemia, such as M1 and M2, which refer to myeloblastic leukemias, and M5, which refers to monocytic leukemias, thus distinguishing APL's unique