The myeloid leukemias
The myeloid leukemias make up 15 to 20 percent of childhood leukemia. Acute myelogenous leukemia (AML), also called acute myeloid or acute myeloblastic leukemia, affects about 500 children and adolescents in the U.S. each year. There are many subtypes of AML that are classified by their appearance under a microscope, by the proteins on the surface of the cells (immunophenotype), by the changes in chromosome number or structure (cytogenetics or karyotype), and by the mutations in certain genes.
The subtypes of AML are:
- Acute undifferentiated leukemia (AML, M0)
- Acute granulocytic leukemia (AML, M1 or M2)
- Acute promyelocytic leukemia (APL, M3)
- Acute myelomonocytic leukemia (AMML, M4)
- Acute monoblastic leukemia (AMOL, M5)
- Acute erythroleukemia (AEL, M6)
- Acute megakaryoblastic leukemia (AMKL, M7)
Each of these types of leukemia originates in young or precursor cells that are supposed to form normal mature blood cells. In acute granulocytic leukemia, the marrow produces too many precursors of granulocytes (called myeloblasts), a type of white blood cell that when mature, fights infections, particularly infections from bacteria. Leukemic myeloblasts, however, cannot mature and they do not fight infections. As the myeloblasts overproduce, they crowd out other blood cells.
In acute promyelocytic leukemia, promyelocytes that are just a bit more mature than the myeloblasts crowd out the normal marrow cells. In acute monoblastic leukemia, the leukemia cell, the monoblast, is the precursor of the monocyte, another type of infection-fighting white blood cell. Myelomonocytic leukemia consists of cells with characteristics of both monoblasts and myeloblasts. In contrast, acute erythroleukemia is a cancer of the young red blood cells, called erythroblasts, and acute megakaryoblastic leukemia is a leukemia involving the platelet-forming cells called megakaryoblasts.
To read more about pediatric leukemia, click here to go to Children’s Hospital of Philadelphia’s Cancer Center.