Monoblast

Scheme electron microscopy. The precursor of this cell is the promonoblast derived from the common stem cell CFU-GM (colony forming unit-granulocyte/monocyte). After proliferation of the promonoblasts they transform into monoblasts (up to 10 μm). The nucleus of the monoblast shows an indentation as well as large nucleolus, the cytoplasm contains few organelles, predominantly polysomes and few electron-dense granules (azurophilic or primary granules i.e. lysosomes) are present.