Repeat bone marrow biopsy and aspirate (Figure 1(a)) showed 64%
myeloblasts which expressed a slightly different immunophenotype than originally (CD13, CD33, CD15, CD58, CD117, and HLA-DR).
Panels (c) and (d) show confluent immature
myeloblasts consistent with myeloid sarcoma.
Bone destruction is attributed to the invasion of leukemic
myeloblasts or an imbalance of osteoblasts and osteoclasts.
They also found that such artificially created elite cells are very similar to white blood cell progenitors in the bone marrow called GMPs or
myeloblasts, which themselves require C/EBPa for their formation.
Promyelocytes and
myeloblasts are not observed (Wright stain, 1000x).
AML is characterized by a higher rate of abnormal hematopoietic stem cells in bone marrow than in MDS, and inefficient production of blood cells and peripheral organ failure due to migrating
myeloblasts. The numbers of patients with AML in the United States and in Japan are estimated to be around 25,000 and 6,000, respectively.
The first, also called erythroleukemia, involves
myeloblasts and rubriblasts (BENNETT et al., 1976).
Myeloid sarcoma, also known as chloroma, extramedullary myeloid tumor or granulocytic sarcoma, is an extramedullary tumor mass consisting of immature myeloid cells and/or
myeloblasts. (1,2) Myeloid sarcoma can occur de novo, concurrently or following the diagnosis of acute myeloid leukemias (AML), myeloproliferative neoplasms (MPN), and myelodysplastic syndromes (MDS).
Bone marrow aspiration revealed hypercellularity, different cell body sizes, diminished or moderate cytoplasms, round or oval nuclei, enhanced nuclear chromatin, and 10%
myeloblasts. Differential flow cytometric analysis demonstrated that the blasts expressed the myeloid antigens CD34, CD13, and CD117.
Visual examination of spleen sections revealed that splenocytes from NOD mice had a tendency to ring-shaped rather than polylobed morphology, indicating presence of granulopoietic stage 1
myeloblasts. C57BL/6 mice had a population of cells displaying the more polylobed morphology, of more mature neutrophils (Figure 5), indicating that relatively more immature granulocytes are present in the spleen and liver of NOD mice.
[sup][32],[37] Increased production of cytokines and expression of adhesion markers such as intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and selectin by endothelial cells enables
myeloblasts to recruit additional
myeloblasts.
One case of AML, however, showed pancytopenia with presence of
myeloblasts in the peripheral blood.
