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Haematology & Oncology

Leukaemia

A group of malignant clonal disorders of blood-forming cells, classified along two axes that decide everything else: cell lineage (myeloid or lymphoid) and tempo (acute, a maturation arrest that fills the marrow with blasts over weeks, or chronic, a slow expansion of maturing cells over years).

In a nutshell

Classify every leukaemia by two axes: lineage (myeloid or lymphoid) and tempo (acute or chronic). Acute disease is a maturation arrest with blasts and rapid marrow failure needing same-day referral; chronic disease is a slow expansion of maturing cells, often found incidentally. The four core diseases are AML, ALL, CML and CLL.

Classic presentation

Either a patient with fatigue, fever and bruising over days to weeks and blasts on the film (acute), or an older adult with an incidental leucocytosis or lymphocytosis on a routine blood count (chronic).

Key points

  • Two axes name the disease: myeloid versus lymphoid (immunophenotype) and acute versus chronic (cell maturity on film and marrow).
  • Acute leukaemia is a maturation arrest: blasts fill the marrow and all three lineages fall together, giving the anaemia, infection and bleeding triad over days to weeks.
  • Chronic leukaemia keeps maturing, so the blood fills with maturing granulocytes (CML) or mature lymphocytes (CLL) and the course is slow and often silent.
  • 20% or more blasts in the marrow defines acute leukaemia; immunophenotyping assigns lineage and cytogenetics subtypes it.
  • Classification decides everything: urgent chemotherapy for AML and ALL, a tyrosine kinase inhibitor for CML, and often watchful waiting for CLL.

First-line investigation

Full blood count and blood film to reveal cytopenias and the maturity of the abnormal cells, followed by bone marrow biopsy with immunophenotyping and cytogenetics to confirm and subtype the leukaemia.

Management

Recognise acute or unstable disease

  • Escalate same day for circulating blasts, suspected APL, bleeding, neutropenic sepsis, leucostasis symptoms or physiological instability.3,2

Confirm lineage and tempo

  • Send FBC and film urgently, then use integrated flow, marrow, cytogenetic and molecular testing through specialist haematology.1,2

Prevent early treatment complications

  • Treat infection and bleeding promptly and use a specialist tumour-lysis prevention and monitoring plan before cytoreduction.6,7

Treat the subtype

  • Use protocol-led AML or ALL treatment, BCR::ABL1-directed therapy for CML, and risk-based monitoring or targeted therapy for CLL.4,5

Monitor response and late effects

  • Document molecular or measurable-residual-disease monitoring, relapse or transformation surveillance, infection advice and survivorship needs.2,4,5

Exam traps

  • Blasts on the film mean acute leukaemia; a high count of mature-looking cells points to a chronic leukaemia, not an acute one.
  • The white cell count can be high, normal or low in acute leukaemia, so a normal count does not exclude it if blasts are seen.
  • Watch and wait is reasonable in early chronic leukaemia but is never appropriate for acute leukaemia.
  • A dangerously high count of mature neutrophils with basophilia and splenomegaly suggests CML, not infection; a reactive leukaemoid reaction lacks the Philadelphia chromosome.

Illustrations

Myeloblasts with Auer rods in acute myeloid leukaemiaBlood film showing numerous immature myeloblasts, including cells with slender Auer rods, illustrating the maturation arrest and blast accumulation of acute myeloid leukaemia.Paulo Henrique Orlandi Mourao, Wikimedia Commons · CC-BY-SA-3.0

Key sources

  1. BSH: Recommendations for laboratory testing of UK patients with acute myeloid leukaemia (UK BSH guidance covering morphology, flow and genetics.)Published 27 Oct 2022
  2. NICE NG47: Haematological cancers: improving outcomes (Integrated diagnostic reporting, specialist MDT care and high-intensity treatment safety pathways.)Published 25 May 2016
  3. NICE NG12: Suspected cancer: recognition and referral (Current UK referral recommendations for suspected leukaemia.)Updated 15 Apr 2026
  4. BSH: Guideline on the diagnosis and management of chronic myeloid leukaemia (UK BSH CML diagnosis, monitoring and treatment guidance.)Published 30 Jul 2020 | Updated 19 Feb 2021
  5. BSH: 2025 guideline for the treatment of chronic lymphocytic leukaemia (Current UK BSH CLL treatment guideline.)Published 9 Oct 2025
  6. BSH: Updated guidelines for the diagnosis and management of tumour lysis syndrome (Current UK tumour-lysis guidance.)Published 3 Sept 2025 | Updated 8 Dec 2025
  7. BNF online (Check current prescribing, interactions, contraindications and monitoring.)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.