Morphologic Characteristics of Erythroid Precursors

Pronormoblast (rubriblast):

• 1% of Nucleated Cells in BM.
• Size = 20-25 μm.
• High N/C ratio (8:1)
• 1-3 faint nucleoli 
• Lacy chromatin 

Basophilic normoblast (prorubricyte):

• 1-3% of nucleated cells in BM.
• Size = 16-18 μm
• Moderate N/C ratio (6:1)
• Indistinct nucleoli
• coarsening chromatin

Polychromatophilic normoblast (rubricyte):

• 13-30% of nucleated cells in BM.
•  Size = 12 - 15 μm
• Low N/C ratio (4:1)
• Chromatin irregular and coarsely clumped
• Eccentric nucleus

Orthochromic normoblast (metarubricyte):

• 1-4% of nucleated cells in BM
• Size = 10 -15 μm
• Low N/C ratio (1:2)

Reticulocyte (new methylene blue stain):

• Size = 7-10 μm
• No N/C ratio because there is no nucleus

Reticulocyte (Wright’s stain):

• Polychromatophilic (diffusely basophilic)

Mature RBC:

• Size = 7 -8 μm
• No nucleus