Minimally differentiated acute myeloblastic leukemia
is a subtype of AML. It is classified as M0 by FAB. It represents 2-3% of all cases of AML. Although minimally differentiated AML was recognized earlier, criteria for FAB M0 were developed in 1991. The blasts in these cases cannot be recognized as myeloid based on morphology and cytochemistry
, but immunophenotyping
demonstrates myeloid antigens.
Cytochemistry and Molecular Features
In acute myeloblastic leukemia (M0), the blasts are agranular and nonreactive when stained for myeloperoxidase
activity, and Auer rods
are not seen. The blasts react with antibodies to myeloperoxidase and antibodies to CD13
, and CD34
. Human leukocyte antigen
(HLA)-DR is positive in most patients. Occasional cases require in situ hybridization
to identify the myeloperoxidase gene315 or genomic profiling for early myeloid-associated genes. Abnormal and unfavorable karyotypes (e.g., loss of the long arm of chromosome 5 (5q-) and 7q-) and higher expression of the multidrug resistance glycoprotein (p170) are frequent. In general, minimally differentiated acute myeloblastic leukemia has a poor prognosis.