myeloblast

An immature cell (10 to 18 μm in diameter) in the granulocytic series, occurring normally in bone marrow, but not in the circulating blood (except in certain diseases). When stained with the usual dyes, the cytoplasm is light blue, nongranular, and variable in amount, sometimes being only a thin rim around the nucleus; the latter is deep purple-blue with finely divided, punctate, threadlike chromatin that is somewhat condensed at the periphery. A few light blue nucleoli are usually present in the nucleus, and these generally disappear as the m. matures into a promyelocyte and then a myelocyte. Myeloblasts ordinarily yield a negative reaction with peroxidase. [myelo- + G. blastos, germ]

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my·e·lo·blast 'mī-ə-lə-.blast n a large mononuclear nongranular bone marrow cell esp one that is a precursor of a myelocyte compare LEUKOBLAST

my·e·lo·blas·tic .mī-ə-lə-'blas-tik adj

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n.

the earliest identifiable cell that gives rise to a granulocyte, having a large nucleus and scanty cytoplasm. It is normally found in the blood-forming tissue of the bone marrow, but may appear in the blood in a variety of diseases, most notably in acute myeloblastic leukaemia. See also granulopoiesis.

• myeloblastic adj.

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my·elo·blast (miґə-lo-blast) [myelo- + -blast] an immature cell found in the bone marrow and not normally in the peripheral blood, the most primitive precursor in the granulocytic series, which develops into the promyelocyte. Myeloblasts have fine, evenly distributed chromatin, several nucleoli, and a nongranular basophilic cytoplasm.