علوم آزمایشگاهی دانشگاه علوم پزشکی تهران

Promyelocyte

Promyelocytes are the second largest stage in the granulocytic series. The large, reddish-purple granules that characterize promyelocytes are nonspecific in that they are shared by the other granulocytes (eosinophils and basophils). These granules are peroxidase positive, and a lipid component reacts with Sudan black stain, providing a second cytochemical reaction for the identification of large mononuclear cells in blood and bone marrow smears. The cell size, 12 to 20 µm, is the same as that of a myeloblast, but the nucleus to cytoplasm ratio is less, usually from 3:1 to 2:1. The chromatin is still fine, but some aggregation is evident. One to three nucleoli are also visible, although these can be obscured by heavy granulation.