Acute monoblastic leukemia
Other Names: Acute myeloblastic leukemia type 5; Acute monocytic leukemia; AML-M5; AML M5
Acute monoblastic leukemia (AML-M5), is one of the most common subtypes of acute myeloid leukemia (AML; see this term) that is either comprised of more than 80% of monoblasts (AML-M5a) or 30-80% monoblasts with (pro)monocytic differentiation (AML-M5b). AML-M5 presents with asthenia, pallor, fever, and dizziness. Specific features of AML-M5 include hyperleukocytosis, propensity for extramedullary infiltrates, coagulation abnormalities including disseminated intravascular coagulation and neurological disorders. Leukemia cutis and gingival infiltration can also be seen. A characteristic translocation observed in AML-M5 is t(9;11).
M5 is associated with characteristic chromosomal abnormalities, often involving chromosome 11, such as t(9;11), affecting the MLL (KMTA2) locus at 11q23; however MLL translocations are also found in other leukemia subtypes. The t(8;16) translocation in AMoL is associated with hemophagocytosis.
In order to fulfill World Health Organization (WHO) criteria for AML-5, a patient must have greater than 20% blasts in the bone marrow, and of these, greater than 80% must be of the monocytic lineage.
A further subclassification (M5a versus M5b) is made depending on whether the monocytic cells are predominantly monoblasts (>80%) (acute monoblastic leukemia) or a mixture of monoblasts and promonocytes (<80% blasts).
By contrast, promonocytes have a more convoluted nucleus, and their cytoplasm may contain metachromatic granules. Monoblasts are typically MPO-negative and promonocytes are MPO variable. Both monoblasts and promonocytes stain positive for non-specific esterase (NSE), however NSE may often be negative.
Immunophenotypically, M5-AML variably express myeloid (CD13, CD33) and monocytic (CD11b, CD11c) markers. Cells may aberrantly express B-cell marker CD20 and the NK marker CD56. Monoblasts may be positive for CD34. Immunophenotyping
- CD4 expression
- CD11b expression
- CD11c expression
- CD13 expression
- CD14 expression
- CD15 expression
- CD33 bright expression
- CD34 positive
- CD36 bright expression
- CD64 bright expression
- CD65 expression
- CD68 expression
- HLA-DR positive
- Lysozyme expression
- KIT (CD117) expression
- MPO expression
Definitive Diagnostic Methods
NIH genetic and rare disease info
Acute monoblastic leukemia is a rare disease.
Latest research - Acute monoblastic leukemia