Haematology · Peripheral smear / marrow (Wright stain)

Auer Rods (Acute Myeloid Leukaemia)

A blast with a thin pink rod in its cytoplasm — an Auer rod, which establishes myeloid lineage and indicates acute myeloid leukaemia (AML).

High-power blood film showing a large blast cell with a thin pink needle-like rod in its cytoplasm
Auer rods in a leukaemic blast (recurrent AML), Wright stain, ×1000.Image: Ed Uthman from Houston, TX, USA, via Wikimedia Commons — CC BY 2.0.

Written & reviewed by: Kinase Medical Team · Last reviewed: 30 September 2026 · Editorial policy

Key features

  • Red-staining, needle- or rod-shaped cytoplasmic inclusions — crystal aggregates of azurophilic (myeloperoxidase-positive) granules.
  • Specific for neoplastic myeloid cells: when present, myeloid lineage is virtually certain.
  • Particularly numerous in acute promyelocytic leukaemia (APL, t(15;17)), which carries a high DIC risk and responds to all-trans retinoic acid.
  • AML is defined by ≥20% myeloid blasts in the marrow (WHO).
  • Bundles of Auer rods in one cell are called faggot cells; rods are also seen in myelodysplastic syndromes and MDS/MPN.
  • Not present in every AML case; rods persisting in blasts after treatment indicate the disease is not in remission.

Differential diagnosis

Differential diagnosis of Auer Rods (Acute Myeloid Leukaemia)
ConditionHow to tell it apart
Acute monocytic leukaemiaMonoblasts usually lack myeloperoxidase and characteristically infiltrate the gums.

How it appears in NEET PG

Blood-film questions show a blast with a pink rod and ask for the diagnosis, the stain it is positive with (myeloperoxidase) or the translocation of the subtype with many rods.

Frequently asked questions

What are Auer rods made of?

Fused, crystallised primary (azurophilic) granules containing myeloperoxidase.

Which leukaemia has the most Auer rods?

Acute promyelocytic leukaemia, where abnormal promyelocytes are packed with granules and rods.

Are Auer rods seen in ALL?

No. They are specific for neoplastic myeloid cells, which is why they help separate AML from lymphoblastic leukaemia.

Sources

  1. Sehgal T, Sharma P. Auer rods and faggot cells: a review. Eur J Haematol 2023 (PubMed)
  2. Robbins Basic Pathology (textbook)
  3. Harrison's Principles of Internal Medicine (textbook)
  4. Pathoma — Fundamentals of Pathology (review text)

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For exam preparation and medical education only — not a substitute for clinical judgement, diagnosis or treatment of any patient.