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

Promyelocyte*


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› Microscopic Features:

• 2-3x larger than a mature RBC
• High nuclear to cytoplasmic ratio (but more cytoplasm than Myeloblast)
• Round Nucleus with immature chromatin (not clumped)
• Nucleoli are present but less prominent than Myeloblasts
• Cytoplasm with primary (azurophilic) granules

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

• PB: None
• BM: Scattered (~2-6%)
• LN: None

› May Resemble:

• Myeloblast
• Myelocyte
• Reactive lymphocyte
• Neurophil with toxic granules

› Differential Diagnoses:

If in blood or increased numbers in bone marrow: Acute promyelocytic leukemia (AKA AML M3) Myeloproliferative Neoplasms (e.g. CML) Leukemoid reactions Post-GCSF therapy

› Classic Immunophenotype:

• CD34-
• CD117+
• HLA-DR-
• CD13+
• CD33+
• CD15-/+

› Cartoon Image:


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› Misc:

• Scattered promyelocytes can be seen in a normal bone marrow but no auer rods are allowed in normal promyelocytes