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Staging of leukemia

Acute leukemia

Two classification systems are used: WHO and FAB. The FAB classification is still the most utilized system. 

Both systems are based on morphological examinations of blood and bone marrow smears.

Photomicrograph of MCG-stained bone marrow from patient with acute myloid leukemia, M3. Click to enlarge the image.

Whichever superior diagnostic technique is applied, there are patients who require a combination of cytochemical, immunological, cytogenetic, and special molecular genetic examinations to achieve the correct diagnosis and prognosis. Such examinations are therefore part of the WHO classification. This classification will eventually replace the FAB classification.

The criteria for making the diagnosis of acute myeloid leukemia is reduced from 30% blasts in the FAB classification to 20% in the WHO classification.

Division of AML according to FAB criteria
M0 – undifferentiated leukemia
M1 – without sign of maturity
M2 – with sign of maturity
M3 – hypergranular promyelocyte leukemia
M4 – myelomonocyte leukemia
M5 – monoblast leukemia
M6 – erythro leukemia
M7 – megakaryoblast leukemia
Division of ALL according to FAB criteria
L1 – cytoplasma-deficient, small blasts
L2 – more heterogenous with emphasis on cytoplasma richness and size
L3 – B-cell blasts with basophile vacuolized cytoplasma 

Chronic leukemia

Photomicrograph of MCG-stained peripheral blood smear from patient with chronic myeloid leukemia. Click to enlarge the image.

Disease progression of chronic myeloid leukemia is separated into three phases.  

Chronic phase



< 15 % blast cells in blood or bone marrow

< 30 % – the sum of blast cells and promyelocytes in blood or bone marrow

< 20 % basophile granulocytes in peripheral blood

Thrombocyte count > 100 x 109/l

Normal or close to normal blood values without immature granulocytes in the blood

Accelerated phase
Blast count between 15–29 % in blood or bone marrow

≥ 30 %, the sum of blast cells and promyelocytes in blood or blood marrow.

≥ 20 % basophile granulocytes in blood

Thrombocyte count < 100 x 109/l, which cannot be explained by treatment  

Often also increasing splenomegaly

new chromosome changes in Ph+ clone

Blast phase
Characterized by >30 % of the cells in blood or bone marrow are blasts

Patients have symptoms of acute leukemia.

Extramedullary illness 

The accelerated phase is usually a short transition phase between the chronic phase and blast phase.

Chronic lymphatic leukemia is characterized by accumulation of small, mature-appearing lymphcytes in blood, bone marrow, and organs. It is common to separate patients into prognostic groups at the time of diagnosis.

Stage division of CLL according to Binet
Criteria Stage
  A B C
Number of involved lymph node regions 0–2 3–5 0–5
Hemoglobin (g/dl) >10 >10 <10
Thrombocytes (109/l) >100 >100 <100
Survival (years) >10 5 2.6

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