- The proerythroblast varies from 12 to 20 μm in diameter and has a large nucleus that occupies most of the cell. The chromatin strands are fine, giving an even reticular appearance. Nucleoli are present. The cytoplasm is intensely basophilic—much more so than is seen in blast cells of the white cell series.

The proerythroblast (A) is the earliest identifiable erythroid precursor in the bone marrow.

Proerythroblast and polychromatic
erythroblasts in the peripheral blood
of a newborn infant with haemolytic
disease of the newborn.
- Sources:
– Microscopic haematology: a practical guide for the laboratory / Gillian Rozenberg
– http://media.mssm.edu