Eosinophils develop from the multipotential myeloid stem cell (CFU-GEMM) which differentiates into eosinophilic progenitor cells (CFU-Eo).
Eosinophilic myeloblasts are produced directly from progenitor cells (CFU-Eo) under the influence of cytokines. The eosinophilic myeloblast matures into an eosinophilic promyelocyte. These cells cannot be distinguished from cells at the same stage in other granulocyte lineages. (See MH034B Neutrophil Development for these earlier stages.)
Eosinophilic myelocyte is the first recognizable precursor of eosinophils.
Large cells (18 to 20 µm diameter)
Round, oval, or indented nucleus (50% of cell) with a coarser, granular pattern of chromatin
Cytoplasm is pale blue
Very eosinophilic, specific granules begin to accumulate