Acute myeloid leukaemia without maturation

The majority of cells are blasts without granulation, only some of them are obvious myeloblasts with granulation (red arrow); unequivocal Auer rods can also be found (not shown in this picture). Blasts constitute ≥ 90% on the non-erythroid cells; more mature cells of neutrophil lineage account for less than 10%.

The myeloid nature of blasts is demonstrated by the positivity of myeloperoxidase, which can be positive in a variable number of blasts but always at least in 3% of them.

The analysis of bone marrow shows AML blasts (purple), T lymphocytes (blue), B lymphocytes (brown) and granulocytes (red). Blasts constitute more than 90% of nuclear cells. Blasts express characteristic markers for a minimal maturation and a low intensity of SS and CD45 (A). Furthermore, they have a positive expression of CD34, CD117 and cMPO (myeloperoxidase), a low expression of CD33 and CD14 and a typical aberrant expression of CD7 (B–D).