Promyelocytes are not normally found in peripheral blood, and their presence indicates severe infection when seen with other immature neutrophils. Many abnormal versions of this cell can be seen in acute promyelocytic leukemia (APL).
Promyelocyte Appearance
Promyelocytes have a basophilic cytoplasm with a perinuclear hof. Azurophilic (primary) granules can be seen. The nucleus is usually round to oval-shaped with nucleoli and relatively fine chromatin.
Lookalikes
Promyelocytes mature into myelocytes, so differentiation between these cells can be difficult. Both cells contain the primary azurophilic granules, but only myelocytes have the pinkish secondary granules.
Quick Summary
- Morphology/Appearance:
- Cytoplasm: Basophilic, Perinuclear Hof
- Granules: Azurophilic (primary)
- Nucleus: Round to Oval-Shaped
- Nucleoli: Present
- Chromatin: Fine
- Clinical Significance:
- Severe Infection
- Acute Promyelocytic Leukemia
- Common Lookalikes:
- Myelocytes which have pink secondary granules
Promyelocyte Gallery
Additional Resources
Authored by Rachel Harper, Medical Laboratory Scientist (ASCP)
Last reviewed: January 2026
For educational and reference purposes only, this is not medical advice.