Childhood Acute Myeloid Leukemia/Other Myeloid Malignancies Treatment (PDQ®): Treatment - Health Professional Information [NCI] - Classification of Pediatric Myeloid Malignancies
In 2002, the WHO proposed a new classification system that incorporated diagnostic cytogenetic information and more reliably correlated with outcome. In this classification, patients with t(8;21), inv(16), t(15;17), and those with MLL translocations, which collectively constituted nearly half of the cases of childhood AML, were classified as "AML with recurrent cytogenetic abnormalities." This classification system also decreased the bone marrow percentage of leukemic blast requirement for the diagnosis of AML from 30% to 20%; an additional clarification was made so that patients with recurrent cytogenetic abnormalities did not need to meet the minimum blast requirement to be considered AML.[9,10,11] In 2008, WHO expanded the number of cytogenetic abnormalities linked to AML classification, and for the first time included specific gene mutations (CEBPA and NPM mutations) in its classification system. (Refer to the WHO classification of myeloid leukemias section of this summary for more information.) Such a genetically based classification system links AML class with outcome and provides significant biologic and prognostic information. With new emerging technologies aimed at genetic, epigenetic, proteomic, and immunophenotypic classification, AML classification will likely evolve and provide informative prognostic and biologic guidelines to clinicians and researchers.
WHO classification of AML
- AML with recurrent genetic abnormalities:
- AML with t(8;21)(q22;q22), RUNX1-RUNX1T1(CBFA/ETO).
- AML with inv(16)(p13;q22) or t(16;16)(p13;q22), CBFB-MYH11.
- APL with t(15;17)(q22;q11-12), PML-RARA.
- AML with t(9;11)(p22;q23), MLLT3-MLL.
- AML with t(6;9)(p23;q34), DEK-NUP214.
- AML with inv(3)(q21;q26.2) or t(3;3)(q21;q26.2), RPN1-EVI1.
- AML (megakaryoblastic) with t(1;22)(p13;q13), RBM15-MKL1.
- AML with mutated NPM1.
- AML with mutated CEBPA.
- AML with myelodysplasia-related features.
- Therapy-related myeloid neoplasms.
- AML, not otherwise specified:
- AML with minimal differentiation.
- AML without maturation.
- AML with maturation.
- Acute myelomonocytic leukemia.
- Acute monoblastic and monocytic leukemia.
- Acute erythroid leukemia.
- Acute megakaryoblastic leukemia.
- Acute basophilic leukemia.
- Acute panmyelosis with myelofibrosis.
- Myeloid sarcoma.
- Myeloid proliferations related to Down syndrome:
- Transient abnormal myelopoiesis.
- Myeloid leukemia associated with Down syndrome.
- Blastic plasmacytoid dendritic cell neoplasm.
The treatment for children with AML differs significantly from that for ALL. As a consequence, it is crucial to distinguish AML from ALL. Special histochemical stains performed on bone marrow specimens of children with acute leukemia can be helpful to confirm their diagnosis. The stains most commonly used include myeloperoxidase, periodic acid-Schiff (PAS), Sudan Black B, and esterase. In most cases the staining pattern with these histochemical stains will distinguish AML from AMML and ALL (see below). This approach is being replaced by immunophenotyping using flow cytometry.
Table 1. Histochemical Staining Patternsa
|M0||AML, APL (M1-M3)||AMML (M4)||AMoL (M5)||AEL (M6)||AMKL (M7)||ALL|
|AEL = acute erythroid leukemia; ALL = acute lymphoblastic leukemia; AML = acute myeloid leukemia; AMKL = acute megakaryocytic leukemia; AMML = acute myelomonocytic leukemia; AMoL = acute monocytic leukemia; APL = acute promyelocytic leukemia; PAS = periodic acid-Schiff.|
|a Refer to theFrench-American-British (FAB) Classification for Childhood Acute Myeloid Leukemiasection of this summary for more information about the morphologic-histochemical classification system for AML.|
|b These reactions are inhibited by fluoride.|
|Nonspecific esterases|| || || || || || || |
| ||Alpha-naphthol acetate||-||-||+b||+b||-||±b||-|
|Sudan Black B||-||+||+||-||-||-||-|