The Acute Leukaemias

The Acute Leukaemias

Ahmad Sh. SilmiMsc Haematology, FIBMS

What Is Acute Leukemia?• The acute leukaemias are a heterogeneous group of malignant disorders,

which are characterized by the uncontrolled clonal proliferation and accumulation of poorly differentiated blast cells in the bone marrow and other tissues.

• Thus replacement of normal bone marrow elements with abnormal (neoplastic) blood cells.

• These leukaemic cells are frequently (but not always) present in the peripheral blood stream. Subsequently there is a raised total blood count and evidence of bone marrow failure (i.e. anaemia, neutoropenia, thrombocytopenia) are ensues.

• In the acute leukaemias the blasts commonly invade reticuloendothelial tissues including the spleen, liver and lymph nodes. They may also invade other tissues, infiltrating any organ of the body.

• If left untreated, leukaemia eventually causes death.

Hematopoieticstem cell

Neutrophils

Eosinophils

Basophils

Monocytes

Platelets

Red cells

Myeloidprogenitor

Lymphoidprogenitor

B-lymphocytesB-lymphocytes

T-lymphocytes

Plasmacells

naïve

ALLALL

AMLAML

Myeloid maturation

myeloblast promyelocyte myelocyte metamyelocyte band neutrophil

MATURATIONMATURATION

Adapted and modified from U Va website

Acute Leukemia

• accumulation of blasts in the marrow

Marrow failure

• neutropenia: infections, sepsis

• anemia: fatigue, pallor

• thrombocytopenia: bleeding

Demographics of Leukemia Patients (2001 Data)

ALL11%

CLL26%

AML31%

CML15%

others17%

Total Reported Cases = 31,500Sources from Leukemia, Lyphoma,

Myeloma Facts 2001

CLL=Chronic Lymphocytic

ALL=Acute Lymphocytic

CML=Chronic Mylogenous

AML=Acute Mylogenous

Acute Leukaemogenesis

• The acute leukaemias are thought to develop as a result of a genetic alteration within a single stem cell in the bone marrow. Which means, a blockage of maturation at certain level; this reveals an abnormal regulatory mechanism, and the cell is incapable for further proliferation and differentiation, but it still has the ability to divide.

• Successive mitotic division in the progeny of the cell produces a clonal population, which once it is sufficient a clonal mass has been achieved, and gives rise to the clinical manifestation of the disease.

differentiation block

enhancedproliferation

AcuteLeukemia+

Gain of function mutations of tyrosine kinases

eg. FLT3, c-KIT mutations N- and K-RAS mutations BCR-ABL TEL-PDGFR

Loss of function of transcription factors needed for differentiation

eg. AML1-ETO CBF-SMMHC PML-RAR

Two-hit model of leukemogenesis

Development of Leukemia in the Bloodstream

Stage 1- Normal Stage 2- Symptoms Stage 3- Diagnosis

Stage 4- Worsening

Stage 5a- Anemia

Stage 5b- Infection

Legend

White Cell

Red Cell

Platelet Blast

Germ Sources from Leukemia, by D. Newton and D. Siegel

Lab evaluation– The lab diagnosis is based on two things

– Finding a significant increase in the number of immature cells in the bone marrow including blasts, promyelocytes, promonocytes (>30% blasts is diagnostic)

– Identification of the cell lineage of the leukemic cells

– Peripheral blood:• Anemia (normochromic, normocytic)• Decreased platlets• Variable WBC count

– The degree of peripheral blood involvement determines classification:

» Leukemic – increased WBCs due to blasts

» Subleukemic – blasts without increased WBCs

» Aleukemic – decreased WBCs with no blasts

Classification of the immature cells involved may be done by:

1- Morphology – an experienced morphologist can look at the size of the blast, the amount of cytoplasm, the nuclear chromatin pattern, the presence of nucleoli and the presence of auer rods (are a pink staining, splinter shaped inclusion due to a rod shaped alignment of primary granules found only in myeloproliferative processes) to identify the blast type:

• AML – the myeloblast is a large blast with a moderate amount of cytoplasm, fine lacey chromatin, and prominent nucleoli. 10-40% of myeloblasts contain auer rods.

Myeloblasts with auer rods

Morphology, cont.

• ALL – in contrast to the myeloblast, the lymphoblast is a small blast with scant cytoplasm, dense chromatin, indistinct nucleoli, and no auer rods

Lymphoblast

FAB• In an attempt to improve the reproducibility and

comparability of the classification process, a grouped of expert haematologists from French, America, and Britian (FAB) collaborated to define a more objective criteria for the classification of acute leukaemias.

• The initial FAB study was based on the examination of more than 200 different cases of acute leukaemia by expert morphologists, in addition, a myeloperoxidase or suddan black stains should be used to facilitate the recognition of myeloblasts.

Classification of leukemiaMain classification

Chronic leukemia Acute leukemia

Lymphoid LymphoidMyeloid Myeloid

FAB

AMLM0M1M2M3M4M5M6M7

L1L2L3

FAB Characterization for ALL

• L1: Homogenous population of small lymphoblasts with scanty cytoplasm and scanty nucleoli. Nucleus

occasionally cleft.

• L2: Heterogeneous population of large lymphoblasts with moderately abundant cytoplasm & or more nucleoli. Nucleus commonly intended or

cleft.

• L3-Burkitt’s type: Homogenous population of large lymphoblasts with prominent nucleoli &

deeply basophilic, vacuolated cytoplasm.

Acute Non-Lymphoblastic LeukaemiaDiagnosisAlternativeBone Marrow Appearance

M0Identified by ultrastructural myeloperoxidase activity or immunophenotyping.

M1AML without maturationMonomorphic with one or more distinct nucleoli, occasional auer rod and at least 3%

myeloperoxidase positivity.M2AML with maturation50% OR > myeloblasts & promyelocytes and

common single auer rod. Dysplastic myeloid differentiation may also be present.

M3APLDominant cell type is promyelocyte with heavy azurophilic granulation. Bundles of Auer rods

confirm diagnosis. Microgranular variant exist (M3v)

M4AMMoLAs M2 but > 20% promonocytes & monocytes.

M5AMoL> 80% monoblasts is poorly differentiated (M5a)

> 80% monoblasts, promonocytes or monocytes is well differentiated (m5b)

M6AEL>50% bizzar, dysplastic nucleated red cells with multinucleate forms and cytoplasmic bridging.

Myeloblasts usually > 30%.

M7AMegLFibrosis, heterogeneous blasts population with cytoplasmic blebs. Platelet peroxidase positive.

Acute leukemias

• Acute lymphoblastic leukemia – – They may be classified on the basis of the cytological

features of the lymphoblasts into;• L1 - This is the most common form found in children and it has

the best prognosis. The cell size is small with fine or clumped homogenous nuclear chromatin and absent or indistinct nucleoli. The nuclear shape is regular, occasionally clefting or indented. The cytoplasm is scant, with slight to moderate basophilia and variable vacuoles.

• L2 – This is the most frequent ALL found in adults. The cell size is large and heterogenous with variable nuclear chromatin and prominent nucleoli. The nucleus is irregular, clefting and indented. The cytoplasm is variable and often moderate to abundant, the basophilia is variable and may be deep, and vacuoles are variable.

ALL-L1 (peripheral Blood)

ALL-L1 (Bone Marrow)

ALL-L2 (peripheral Blood)

ALL-L2 (Bone Marrow)

Acute leukemias

• L3 – This is the rarest form of ALL. The cell size is large, with fine, homogenous nuclear chromatin containing prominent nucleoli. The The nucleus is regular oval to round. The cytoplasm is moderately abundant and is deeply basophilic and vacuolated.

ALL-L3 (peripheral Blood)

ALL-L3 (Bone Marrow)

Acute leukemias

– Incidence – ALL is primarily a disease of young children (2-5 years), but it can also occur in adults

– Clinical findings – pancytopenia with resulting fatigue, pallor, fever, weight loss, irritability, anorexia, infection, bleeding, and bone pain.

– L1 occurs in children, L2 in adults, and L3 is called Burkitts leukemia

Acute leukemias

– Prognosis – age, WBC count, and cell type are the most important prognostic indicators

• Patients younger then 1 and greater than 13 have a poor prognosis

• If the WBC count is < 10 x 109/L at presentation, the prognosis is good; If the WBC count is > 20 x 109/L at presentation the prognosis is poor

• T cell ALL (more common in males) has a poorer prognosis than any of the B cell ALLs which have a cure rate of 70%

Acute leukemias

• Acute myeloid leukemia (also called acute granulocytic leukemia) – classification depends upon– Bone marrow blast morphology– Degree of cell maturation– Cytochemical stains– Immunophenotyping– AML is divided into 7 different classifications:

• M1 – myeloblastic without maturation – The bone marrow shows 90% blasts and < 10%

promyelocytes– The disease occurs in older adults

AML – M1

• Note the myeloblasts and the auer rod:

Acute leukemias

• M2 – myeloblastic with maturation– The bone marrow shows 30-89% blasts and > 10%

promyelocytes;– This is characterized by an 8,21 chromosomal translocation – This occurs in older adults

• M3 – hypergranular promyelocytic – This form of AML has a bone marrow with >30% blasts– Is more virulent than other forms – Occurs with a medium age of 39– The WBC count is decreased– Treatment causes a release of the granules and may send

the patient into disseminated intravascular coagulation and subsequent bleeding

– It is characterized by a 15,17 chromosomal translocation

AML – M2

• Note myeloblasts and hypogranulated PMNs:

AML – M3

• Note hypergranular promyelocytes:

Acute leukemias

• M3m – hypogranular promyelocytic – – The bone marrow has > 30% blasts

– The WBC count is increased.

– Like the M3 type, treatment causes a release of the granules and may send the patient into disseminated intravascular coagulation and subsequent bleeding and

– It is characterized by a 15,17 translocation

• M4 – acute myelomonoblastic leukemia – Both myeloblasts and monoblasts are seen in the bone

marrow and peripheral blood

– Infiltration of extramedullary sites is more common than with the pure granulocytic variants

AML – M3m

• Note hypogranular promyelocytes:

AML – M4

• Note monoblasts and promonocytes:

Acute leukemias

• M5 – acute monoblastic leukemia – >80% of the nonerythroid cells in the bone marrow are monocytic– There is extensive infiltration of the gums, CNS, lymph nodes and

extramedullary sites– This form is further divided into

» M5A - Poorly differentiated (>80% monoblasts)» M5B - Well differentiated (<80% monoblasts)

• M6 – erythroleukemia – This is rare and is characterized by a bone marrow having a

predominance of erythroblasts– It has 3 sequentially morphologically defined phases;

» Preponderance of abnormal erythroblasts» Erythroleukemia – there is an increase in both erythroblasts and

myeloblasts» Myeloblastic leukemia – M1, M2, or M4

– Anemia is common

AML – M5A

• Note monoblasts:

AML-M5B

• Note monoblasts, promonocytes, and monocytes:

AML – M6

• Note M1 type monoblasts

Acute leukemias

• M7 - Acute megkaryoblastic leukemia– This is a rare disorder characterized by extensive

proliferation of megakaryoblasts, atypical megakaryocytes and thrombocytopenia

2- The Cytochemistry

______________________ALL____________AML__________

• Myeloperoxidase - +• Suddan black - +• Non-specific esterase - + in M4, M5• Periodic acid Schiff (PAS) + in c-ALL + in M6• Acid phosphatase + in T-ALL + in M6

3- The Immunological

• Immunologic markers (immunophenotyping) – these are used mainly for lymphocytes, i.e., for determining B cell or T cell lineage. These tests rely on antibodies made against specific surface markers. They constitute what we would call the primary antibody and in an indirect assay they are allowed to react with the cells and unbound antibody is then washed away. Fluorescently labeled antibody (secondary antibody) against the primary antibody is added and allowed to react and then unbound secondary antibody is washed away. The cells are then sent through a flow cytometer that will determine the number of cells that have a fluorescent tag and which are thus positive for the presence of the surface marker to which the primary antibody was made. In a direct assay, the primary antibody is fluorescently labeled.

Direct versus indirect labeling of antigens

Flow cytometer

Terminal deoyxtidyl transferase

• This is a unique DNA polymerase present in stem cells and in precursor B and T lymphoid cells. High levels are found in 90% of lymphoblastic leukemias. It can also be detected using appropriate antibodies and flow cytometry.

3- Classification upon The Immunological Approach

• First: The AML FAB classification :

It has revealed that the blasts are usually CD13+, CD33+ and TdT-. Special antibodies are helpful in AML M6 and M7which show that M6 has glycophorin A + and M7 has CD41,42,61+.

Second: The ALL-FAB classification is: • Precursor B-ALL which is CD19+, cytoplasmic CD22+

and TdT+, includes three subtypes, common-ALL which is CD10+, null type which is CD10- and pre-B-ALL which shows intracytoplasmic m chains ( and may be CD10+ 0r CD10- ).

• B-ALL which shows surface immunoglobulin (Ig) and TdT-.

• T-ALL which shows T-cell antigens CD7+, cytoplasmic CD3+ and TdT+. 

• B-ALL usually corresponds to the morphological L3 type whereas the CD10+, null, pre-B or T types may all be L1 or L2 and are morphologically indistinguishable.

B cell maturation

T cell maturation

4- Cytogenetics• Cytogenetics – cytogenetics studies can now be used for

diagnosis and for prognosis of hematologic malignancies.

– Many leukemias (and lymphomas) are characterized by specific chromosomal abnormalities, including specific translocations and aneuploidy. The specific type of malignancy can be identified based on the specific abnormality or translocation. These may be identified by

» Looking at the karyotypes of the chromsomes from the abnormal cells

» DNA based tests – these tests are very useful for following the course of the disease

– A normal karyotype is usually associated with a better prognosis.

Chromosomal translocation

Chromosome karyotyping

Type of Leukaemia

Chromosomal AbnormalityFAB Type

ALLt (9;22 ) L1,L2

Pre-B ALL t (1;19 ) L1

B ALL t (8;14 ) t (8;22)

t (2;8 ) L3

T ALL t (11;14) L1,L2

AMLt (8;21) M2

APLt (15;17) M3

AmoLdel/t (11) M5

AMMoLinv16,and t (16;16) M4

AELt (8;16) M6

4- Cytogenetics

Pathophysiology of the Acute Leukaemias

Acute leukaemia causes morbidity and mortality through three general mechanisms:

• Deficiency in normal blood cell number or function.

• Invasion of vital organs with impairment of organ function.

• Systemic disturbances shown by metabolic imbalance.

First: Deficiency in normal blood cell number or function

• Infection

• Haemorrhage

• Anaemia

Constitutional symptoms

• fever and sweats common

• weight loss less common

2nd:Infiltration of tissues/organs

• enlargement of liver, spleen, lymph nodes

• gum hypertrophy

• bone pain

• other organs: CNS, skin, testis, any organ

Gum hypertrophy

A

B

C

Chloromas

NEJM 1998

Leukostasis

• Leukostatic tumours accumulation of blasts in microcirculation with impaired perfusion

• lungs: hypoxemia, pulmonary infiltrates

• CNS: stroke

• only seen with WBC >> 50 x 109/L (Hyperleucocytosis )

Sanctuary site relapse• Leukaemic infiltration of the testes and

meninges provide an effective sanctuary for resident laeukaemic blasts because cytotoxic drugs poorly penetrate them.

• This provides a source for relapse.

• Meningeal and testicular relapse are most commonly seen in childhood ALL.

3rd:Metabolic Disturbances

• hyponatraemia is relatively common in ANLL secondary to the production of a vasopressin-like substance by myeloblasts.

• Hypokalaemia is also common, especially in AMMoL and AmoL secondary to the renal damage.

• Spontaneous lysis of blast cells causes the release of abnormally large amounts of purines into the plasma. This results to an increase uric

acid or hyperuricaemia. This abnormality may be severe enough to require dialysis, particularly where renal damage is present.

• Several of the cytotoxic drugs are nephrotoxic and therefore may increase the severity of minor metabolic disturbances secondary to massive cell lysis.

Laboratory features

• WBC usually elevated, but can be normal or low

• blasts in peripheral blood

• normocytic anemia

• thrombocytopenia

• neutropenia

• DIC

Bone marrow in acute leukemia

• necessary for diagnosis

• useful for determining type

• useful for prognosis

• Acute leukemias are defined by the presence of > 20% blasts in bone marrow (% of nucleated marrow cells)

Distinguishing AML from ALL

• light microscopy– AML: Auer rods, cytoplasmic granules– ALL: no Auer rods or granules.

• flow cytometry

• special stains (cytochemistry)

AML

AML

Auer rods in AML

ALL