Proerythroblast- The first recognizable cell in the erythroid series. May be larger (14- 19u) than stem cell. Cytoplasm basophilic. Does not possess cytoplasmic granules. Large, round nucleus occupying 80% of cell volume. Finely dispersed chromatin with little condensation or clumping; has 1-2 prominent nucleoli.
Basophilic Erythroblast- Smaller (12-17u) cell with no granules in deeply basophilic cytoplasm. With each mitotic division, basophilia of cytoplasm decreases due to presence of hemoglobin. Nucleus has coarser, checkerboard staining chromatin than proerythroblast; nucleoli can no longer be seen.
*Polychromatophilic Erythroblast- Smaller (10-12u) cell (arrow). Varying amounts of hemoglobin cause cytoplasm to stain a mixture of blue, violet, and gray. Nucleus has heavy, coarse, dark chromatin.