As mentioned, one of the critical first steps in diagnosis is whether the neoplastic disorder appears acute or chronic. Count the percentage of blasts in the peripheral blood smear and the bone marrow smear to determine this. A general guideline is that if 20% or more blasts are found in one or both of these specimens, it is acute leukemia. This is a crucial distinction between AML and chronic myeloid disorders (e.g., myelodysplastic syndromes (MDS) and myeloproliferative disorders (MPD), which may also be referred to as myeloproliferative neoplasms (MPN)).
The top image to the right shows numerous blasts in a blood smear of AML. Note the characteristic large nuclei with loose, lacey chromatin, high nuclear/cytoplasmic ratio, and the presence of nucleoli. Also, there are few representatives of other stages of maturation. Contrast this to the smear below, which is from a patient with chronic myeloid leukemia (CML). Note that there are fewer blasts and more mature cells. Several maturation stages, such as myelocytes, metamyelocytes, and segmented neutrophils, can be seen.
