Morphologic characteristics of the different stages of granulocytic maturation in wild-type mice. Images are of Giemsa-stained (A-E) BM touch preparations and (F) PB smears. The series of pictures from A to F represent the granulocytic differentiation process from the most immature precursors to the most mature form. (Ai-Aii) Myeloblasts have oval nuclei with fine chromatin and distinct nucleoli. Some (Bi-Bii) promyelocytes start to show a small, central clearing in the nucleus that indicates the beginning of the maturation process. The granules in murine promyelocytes are difficult to discern in comparison with their human counterpart. The nuclear clearing enlarges with increasing differentiation, transforming the nucleus to ring-like structures in (Ci-Ciii) myelocytes, (Di-Dii) metamyelocytes, and (Ei-Eiv) band cells, where the string-like form is thinnest. The nuclei of mature neutrophils are most often (Fi-Fii) curled/ringed or (Fiii-Fv) twisted but can also be (Fvi-Fviii) fully segmented. Arrows point to filaments of chromatin separating nuclear segments; arrowheads point to nuclear folds. Of note, myelocytes and metamyelocytes may be difficult to distinguish from immature monocytes because all may have ring-shaped nuclei and a pale blue cytoplasm. Magnification: ×60. Scale bars, 10 μm for all images.