Primary Hematopoietic and Lymphoid Tissue ›› Bone Marrow ›› Normal

Pronormoblast*


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› Microscopic Features:

• 3-4x larger than a mature RBC
• High nuclear to cytoplasmic (N/C) ratio
• Round Nucleus with immature chromatin (not clumped)
• Prominent nucleoli
• Cytoplasm is scant and light blue in color

› Normal % blood-PB, marrow-BM, lymphoid tissue-LN:

• PB: None
• BM: Rare scattered
• LN: None

› May Resemble:

• Myeloblast [Compare]
• Basophilic normoblast [Compare]
• Monoblast [Compare]

› Differential Diagnoses:

Increased in: Erythroid Leukemia (AML M6) Polycythemia Vera Reactive Erythroid Hyperplasia

› Classic Immunophenotype:

• CD45 dim+
• CD117 +
• CD235a (Glycophorin A) -
• CD71+
• Ecadherin+
• Aldehyde dehydrogenase+
• Carbonic Anhydrase I+

› Cartoon Image:


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› Misc:

• In normal marrow they comprise 1-2% of the total nucleated cells which is approximately 2-3% of the nucleated red blood cell precursors.Note: As Erythroid precursors mature, the color of their cytoplasm changes from blue to gray to red-orange (this is due to the increase in the number of hemoglobin molecules within the red cells as they mature). Additionally, the nucleus of the red blood cell becomes more dense as it matures and eventually excretes from the cell, forming the mature RBC.