Classification of acute myelogenous leukemia
Acute myelogenous leukemia (AML) starts in abnormal myeloid stem cells. Myeloid stem cells normally develop into red blood cells (also called erythrocytes), white blood cells (either granulocytes or monocytes) or platelets (also called megakaryocytes).
AML is usually classified by the World Health Organization (WHO) system or the French-American-British (FAB) system. Rarely, acute leukemia may have characteristics of both AML and acute lymphocytic leukemia (ALL). These rare leukemias are referred to as mixed phenotype acute leukemias (MPAL).
WHO classification system @(Model.HeadingTag)>
The WHO system is newer than FAB. It uses cell characteristics and genetics to classify AML into several broad categories.
There are many chromosome abnormalities seen in AML. Common abnormities include:
translocation (part of a chromosome is transferred to another chromosome) of chromosomes 8 and 21, 15 and 17 or 9 and 11
inversion of chromosome 16
deletion of part or all of chromosome 5 or 7
an extra chromosome 8 (called trisomy 8)
Some people with AML have changes, or mutations, in certain genes, including:
FMS-like tyrosine kinase 3 (FLT3) gene
nucleophosmin (NPM1) gene
overexpression of the ERG gene
The WHO system uses these chromosome abnormalities and gene mutations, along with other factors, to classify AML as the following subtypes.
AML with certain genetic abnormalities @(Model.HeadingTag)>
WHO uses specific genetic abnormalities to classify the following types of AML:
AML with a translocation between chromosomes 8 and 21
AML with abnormal
eosinophilsand a translocation or inversion in chromosome 16
AML with changes in chromosome 11
APL (M3), which usually has a translocation between chromosomes 15 and 17
Therapy-related AML @(Model.HeadingTag)>
This type of AML is related to previous chemotherapy with an alkylating drug or radiation therapy.
AML, not otherwise classified @(Model.HeadingTag)>
This classification is used for AML that does not fall into one of the other categories. This group is classified in a similar way to the FAB system and includes:
AML with minimal differentiation (FAB M0)
AML without maturation (FAB M1)
AML with maturation (FAB M2)
acute myelomonocytic leukemia (AMML) (FAB M4)
acute monocytic leukemia (FAB M5)
acute erythroid leukemia (FAB M6)
acute megakaryoblastic leukemia (FAB M7)
acute basophilic leukemia (FAB M2Baso)
acute panmyelosis with
myelofibrosis chloroma(also known as extramedullary leukemia or granulocytic sarcoma or myeloid sarcoma)
FAB classification system @(Model.HeadingTag)>
The FAB system is based mainly on how the leukemia cells, or blasts, look under the microscope. The AML is classified based on the type of cell from which the leukemia developed and how mature the cells are.
Unlike the WHO system, the FAB system does not include chromosome abnormalities.
|M0||AML with minimal differentiation|
|M1||AML without maturation|
|M2||AML with maturation|
|M3||acute promyelocytic leukemia (APL)|
|M4||acute myelomonocytic leukemia (AMML)|
|M4eos||acute myelomonocytic leukemia with eosinophilia|
|M5||acute monocytic, or monoblastic, leukemia|
|M6||acute erythroid leukemia, or erythroleukemia|
|M7||acute megakaryocytic, or megakaryoblastic, leukemia|
Mixed phenotype acute leukemia @(Model.HeadingTag)>
Sometimes the leukemia cells are considered mixed phenotype or mixed lineage because they have both myeloid and lymphoid characteristics. The leukemia cells may have both myeloid and lymphoid features on the same cell, or some leukemia cells have myeloid features and other leukemia cells have lymphoid features. Mixed phenotype acute leukemias (MPAL) are a special category of acute leukemias using the WHO classification system.
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National Cancer Institute. Adult Acute Myeloid Leukemia Treatment (PDQ®) Health Professional Version. Bethesda, MD: National Cancer Institute; 2014: http://www.cancer.gov.
Tuzner NN, Bennett JM . Classification of the acute leukemias: cytochemical and morphologic considerations. Wiernik PH, Goldman JM, Dutcher JP & Kyle RA (eds.). Neoplastic Diseases of the Blood. 5th ed. Springer; 2013: 16: pp. 213-239.