Acute promyelocytic anaemia is characterized by the presence of atypical promyelocytes and a t(15;17) translocation, resulting in a PML-RARA fusion. It is often associated with pancytopenia and disseminated intravascular coagulation. Both hypergranlar and hypogranular variants exist.

Acute Promyelocytic Leukaemia (APML)
Abnormal promyelocyte from a patient with acute promyelocytic leukaemia (APML), showing azurophilic granules, Auer rodes and a bilobed nucleus with prominent nucleoli.
Acute Promyelocytic Leukaemia (APML)
Abnormal promyelocyte from a patient with acute promyelocytic leukaemia (APML), showing numerous Auer rods and azurophilic granules, which almost completely obscure the cellular morphology.
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Blood Film Features:

  • Typically, the patient is pancytopaenic.
  • Atypical promyelocytes:
    • Hyper-granular promyelocytes: large cells with bilobed nucleus, cy­toplasm parked with azurophilic granules
    • “Faggot” cells: atypical promyelocytes with numerous Auer roads
    • Hypo-granular promyelocytes: large cells with bilobed nucleus, absence of granules

Other features to look for:

  • White blood cell count may be low or only slightly elevated
  • Marked thrombocytopenia
  • Schistocytes (concurrent disseminated intravascular coagulation)
Acute Promyelocytic Leukaemia (APML)
Bone marrow aspirate from a patient with acute promyelocytic leukaemia (APML), showing numerous hypergranular promyelocytes and a classic “buttock” cell with a bilobed nucleus (red arrow).
Acute Promyelocytic Leukaemia (APML)
Bone marrow aspirate from a patient with acute promyelocytic leukaemia (APML), showing numerous hypergranular promyelocytes with prominent Auer rods (blue arrows) and a classical “buttock” cell with a bilobed nucleus and prominent nucleoli (red arrow).
Acute Promyelocytic Leukaemia (APML)
Bone marrow aspirate from a patient with acute promyelocytic leukaemia (APML), showing numerous hypergranular promyelocytes, including one with very prominent Auer rods (blue arrow), and an abnormal promyelocyte with less cytoplasmic granules (red arrow). The large size, prominent nucleolus and bilobed nucleus identify it as a promyelocyte.
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Bone Marrow Features:

  • Bone marrow is usually hypercellular
  • Maturation arrest at the promyelocyte stage, commonly with Auer rods and azurophilic granules
  • Monocyte lineage < 20% of bone marrow cells

Other features to look for:

  • Atypical promyelocytes (as above)
  • Cytochemistry: Myeloperoxidase  – Strongly positive, Sudan Black – Strongly positive

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