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

Promyelocyte with Auer Rods*


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› Microscopic Features:

• 3-4x larger than a mature RBC
• High nuclear to cytoplasmic ratio
• Round Nucleus with immature chromatin (not clumped)
• Prominent nucleoli
• Cytoplasm is not as scant as myeloblast, gray to pale blue with primary granules
• Multiple Auer rods may be seen as well

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

• PB: None
• BM: None
• LN: None

› May Resemble:

• Myeloblast [Compare]
• Myeloblast with auer rod [Compare]
• Pronormoblast [Compare]
• Lymphoblast [Compare]
• Monoblast [Compare]
• Reactive lymphocyte [Compare]

› Differential Diagnoses:

If in blood or in bone marrow: Acute Promyelocytic Leukemia (APL)

› Classic Immunophenotype:

• CD34-
• CD117+
• HLA-DR-
• CD13+
• CD33+
• (they may have immunophenotypic aberrancies such as gain of CD56, etc.)

› Cartoon Image:


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for direct comparison
› Misc:

• Promyelocyte with multiple Auer rods are called a "Faggot cell" (Faggot meaning "Bundle of Sticks", the numerous auer rods resemble such)