Proerythroblast

A proerythroblast (or rubriblast, or pronormoblast) is the earliest of four stages in development of the normoblast.

In histology, it is very difficult to distinguish it from the other "-blast" cells (lymphoblast, myeloblast, monoblast, and megakaryoblast). The cytoplasm is blue in an H&E stain, indicating that it is basophilic.