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

Megaloblastoid Nucleated RBC*


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› Microscopic Features:

• Abnormally Large in size for the stage of maturation (i.e. megaloblastoid)
• Nucleus is round and may be less mature for stage of maturation

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

• PB: None
• BM: None
• LN: None

› May Resemble:

• Pronormoblast [Compare]
• Basophilic normoblast [Compare]
• Myeloblast [Compare]
• Monocyte [Compare]

› Differential Diagnoses:

B12 or Folate deficiency Myelodysplastic syndrome Acute Myeloid Leukemia Chemotherapy-induced (e.g.Methotrexate)

› Classic Immunophenotype:

• CD45-
• CD117-
• CD235a (Glycophorin A) dim+
• CD71+
• Note: The immunoprofile can be variable and may show aberrancies

› Cartoon Image:


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› Misc:

• Megaloblastoid changes are also commonly noted in non-neoplastic disorders as well (e.g. B12 or Folate deficiency). Hence, interpretation of such findings should be done with extreme caution and always be interpreted in the correct context.