megakaryoblast


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megakaryoblast

 [meg″ah-kar´e-o-blast″]
the earliest cytologically identifiable precursor in the thrombocytic series, which matures to form the promegakaryocyte.

meg·a·kar·y·o·blast

(meg'ă-kar'ē-ō-blast'),
The precursor of a megakaryocyte.
Synonym(s): megacaryoblast

megakaryoblast

The most immature cell of the megakaryocytic series, which is round or ovoid, and large but variably sized (7–35 µm in diameter; those measuring < 15 µm are termed micromegakaryoblasts). The nuclei are round or oval, contain 1+ nucleoli and have a coarse granular pattern; cytoplasm is scant, blue, agranular, often rims the nucleus, occasionally with several small, blunt, budding peripheral protrusions. Megakaryoblasts are normally found only in the marrow, but may be seen in blood smears with myeloproliferative disorders, especially postsplenectomy.

meg·a·kar·y·o·blast

(meg'ă-kar'ē-ō-blast)
The precursor of a megakaryocyte.
References in periodicals archive ?
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%).
The megakaryoblasts 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.