Color Atlas of Hematology - Practical Microscopic and Clinical ...

36Normal Cells of the Blood and Hematopoietic OrgansPartly Mature White Cell Precursors: Myelocytes andMetamyelocytesMyelocytes are the direct product of promyelocyte mitosis and are alwaysclearly smaller than their progenitors. The ovoid nuclei have a bandedstructure; the cytoplasm is becoming lighter with maturation and in somecases acquiring a pink tinge. A special type of granules, which no longerstain red like the granules in promyelocytes (“specific granules,” peroxidase-negative),are evenly distributed in the cytoplasm. Myelocyte morphologyis wide-ranging because myelocytes actually cover three differentvarieties of dividing cells.Metamyelocytes (young granulocytes) are the product of the final myelocytedivision and show further maturation of the nucleus with an increasingnumber of stripes and points of density that give the nuclei a spottedappearance. The nuclei slowly take on a kidney bean shape and have someplasticity. Metamyelocytes are unable to divide. From this stage on, onlyfurther maturation of the nucleus occurs by contraction, so that the distinctions(between metamyelocytes, band neutrophils, and segmentedneutrophils) are merely conventional, although they do relate to the varying“maturation” of these cell forms.Diagnostic Implications. Like their precursors, myelocytes and metamyelocytesnormally appear in the peripheral blood only during increasedcell production in response to stress or triggers, especially infections (foran overview of possible triggers, see p. 112). Under these conditions, theyare, however, more abundant than myeloblasts or promyelocytes.