myeloblast, monoblast, erythroblast and megakaryoblast
that accumulate in the marrow and interfere with production of blood cells.
MKs undergo a unique maturation process including megakaryoblast
formation and polyploidization to produce proplatelets (Figure 6).
A case report by Pelloso et al5 of a 25-year-old woman who presented with findings suggestive of leukemia raised a differential diagnosis of acute megakaryocytic leukemia with t(9;22)(q34;11) and megakaryoblast
crisis as first-time presentation of CML.
Acute megakaryoblastic leukemia (AMKL) is a subtype of acute myeloid leukemia, a rare heterogenous malignancy in adults and more frequent in children, characterized by abnormal megakaryoblasts
that are immunophenotypically positive for CD41, CD42b and CD61.
Bone marrow biopsy revealed hypocellular marrow with loss of megakaryocytes and megakaryoblasts
. The patient died shortly after the clinical diagnosis from intracranial haemorrhage as a complication of severe thrombocytopenia.
Other findings included hemosiderosis (21%), dysplasia of myeloid lineage (17%), dysplasia of erythroid lineage (13%), myelophthia (17%), necrosis (17%), moderate lymphocytes (17%), a marked quantity of segmented neutrophils (8.3%), megakaryoblasts
(8.3%), and blasts (8.3%).
were markedly reduced with reactive plasmacytosis.
The "preleukemic" phase manifests at, or soon after, birth with circulating megakaryoblasts
that are clonal in origin.
Diagnostic criteria for immune thrombocytopenic purpura (ITP) was platelet count of <150,000/[mm.sup.3] and normal or increased number of megakaryocytes and/or megakaryoblasts
on marrow smear.
The peripheral blood and bone marrow blasts in TAM have basophilic cytoplasm with cytoplasmic blebbing, suggestive of megakaryoblasts
.2 Blasts in TAM display a characteristic immunophenotype.9 In most cases the blasts are positive for CD34, CD56, CD117, CD13, CD33, CD7, CD4 (dim), CD4, CD42, TPO-R, CD36, CD61 and CD71.The blasts are negative for MPO, CD15, CD14 and glycophorin A.
Blasts refer to myeloblasts, lymphoblasts, monoblasts, promonocytes, and megakaryoblasts
Leukemic cells in transient leukemia typically have features of megakaryoblasts
. Cell size varies from 15 to 20 [micro]m.