INTRODUCTION TO LEUKEMIAAcute leukemias

INTRODUCTION TO LEUKEMIA

Leukemia is a malignant disease characterized by unregulated proliferation of one cell type. It may involve any of the cell lines or a

stem cell common to several cell lines.Leukemias are classified into 2 major

groups Chronic in which the onset is insidious, the

disease is usually less aggressive, and the cells involved are usually more mature cells

Acute in which the onset is usually rapid, the disease is very aggressive, and the cells involved are usually poorly differentiated with many blasts.

INTRODUCTION TO LEUKEMIA Both acute and chronic leukemias are further

classified according to the prominent cell line involved in the expansion: If the prominent cell line is of the myeloid series it is

a myelocytic leukemia (sometimes also called granulocytic)

If the prominent cell line is of the lymphoid series it is a lymphocytic leukemia

Therefore, there are four basic types of leukemiaAcute myelocytic leukemia – AML- (includes

myeloblastic, promyelocytic, monocytic, myelomonocytic, erythrocytic, and megakaryocytic)

Acute lymphocytic leukemia – ALL- (includes T cell, B cell, and Null cell)

Chronic myelocytic leukemia – CML - (includes myelocytic and myelomonocytic)

INTRODUCTION TO LEUKEMIAChronic lymphocytic leukemia – CLL - (includes

plasmocytic {multiple myeloma}, Hairy cell, prolymphocytic, large granular cell lymphocytic, Sezary’s syndrome, and circulating lymphoma)

Etiology – the exact cause is frequently not known, but predisposing factors are known: Host factors

Some individuals have an inherited increased predisposition to develop leukemia

There is an increased incidence in those with an inherited tendency for chromosome fragility or abnormality or those with increased numbers of chromosomes (such as Down’s syndrome). Many of these diseases are characterized by

chromosomal translocations.

INTRODUCTION TO LEUKEMIA There is an increased incidence in those with

hereditary immunodeficiencies. There is an increased incidence in those with chronic

marrow dysfunction such as those with myeloproliferative diseases, myelodysplastic syndromes, aplastic anemia, or paroxsymal nocturnal hemoglobinuria.

Environmental factors: Exposure to ionizing radiation Exposure to mutagenic chemicals and drugs Viral infections

INTRODUCTION TO LEUKEMIA

IncidenceAcute leukemias can occur in all age groups ALL is more common in children AML is more common in adults

Chronic leukemias are usually a disease of adults CLL is extremely rare in children and unusual

before the age of 40 CML has a peak age of 30-50

INTRODUCTION TO LEUKEMIA Comparison of acute and chronic leukemias: Acute ChronicAge all ages usually adultsClinical onset sudden insidiousCourse (untreated) 6 mo. or less 2-6 yearsLeukemic cells immature >30% blasts more mature

cellsAnemia prominent mildThrombocytopenia prominent mildWBC count variable increasedLymphadenopathy mild present;often

prominentSplenomegaly mild present;often

prominent

INTRODUCTION TO LEUKEMIA

Acute leukemia – Is a result of:

Malignant transformation of a stem cell leading to unregulated proliferation and

Arrest in maturation at the primitive blast stage. Remember that a blast is the most immature cell that can be recognized as committed to a particular cell line.

Clinical features Leukemic proliferation, accumulation, and

invasion of normal tissues, including the liver, spleen, lymph nodes, central nervous system, and skin, cause lesions ranging from rashes to tumors.

A humoral mediator from the leukemic cells may inhibit proliferation of normal cells.

INTRODUCTION TO LEUKEMIA

Failure of the bone marrow and normal hematopoiesis may result in pancytopenia with death from hemorrhaging and infections.

Lab evaluationThe 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

INTRODUCTION TO LEUKEMIA

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

The degree of peripheral blood involvement determines classification:Leukemic – increased WBCs due to blastsSubleukemic – blasts without increased WBCsAleukemic – decreased WBCs with no blasts

Classification of the immature cells involved may be done by:

INTRODUCTION TO LEUKEMIA 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

INTRODUCTION TO LEUKEMIA ALL – in contrast to the myeloblast, the lymphoblast

is a small blast with scant cytoplasm, dense chromatin, indistinct nucleoli, and no auer rods

INTRODUCTION TO LEUKEMIA Cytochemistry – help to classify the lineage of a

leukemic cell (myeloid versus lymphoid) Myeloperoxidase – is found in the primary granules

of granulocytic cells starting at the late blast stage. Monocytes may be weakly positive.

SUDAN BLACK Sudan black stains phospholipids, neutral fats and

sterols found in primary and secondary granules of granulocytic cells and to a lesser extent in monocytic lysosomes. Rare positives occur in lymphoid cells

NONSPECIFIC ESTERASE Nonspecific esterase – is used to identify monocytic

cells which are diffusely positive. T lymphocytes may have focal staining

ACID PHOSPHATASE Acid phosphatase may be found in myeloblasts and

lymphoblasts. T lymphocytes have a high level of acid phosphatase and this can be used to help make a diagnosis of acute T-lymphocytic leukemia.

LEUKOCYTE ALKALINE PHOSPHATASE

Leukocyte alkaline phosphatase – is located in the secondary granules of segmented neutrophils, bands and metamyelocytes. The LAP score is determined by counting 100 mature neutrophils and bands. Each cell is graded from 0 to 5. The total LAP score is calculated by adding up the scores for each cell.

LEUKOCYTE ALKALINE PHOSPHATASE

INTRODUCTION TO LEUKEMIA 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

B or T Cell marker

B or T cell specific Ab

B or T cell specific Ab

B or T Cell marker

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.

INTRODUCTION TO LEUKEMIA 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 byLooking at the karyotypes of the chromsomes

from the abnormal cellsDNA based tests – these tests are very useful for

following the course of the diseaseRT-PCRSouthern blotting

A normal karyotype is usually associated with a better prognosis.

CHROMOSOMAL TRANSLOCATION

CHROMOSOME KARYOTYPING

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 with variable basophilia and variable vacuoles.

ALL-L1

ALL-L2

ACUTE LEUKEMIAS L3 – This is the rarest form of ALL.

The cell size is large, with fine, homogenous nuclear chromatin containing prominent nucleoli.

The nucleus is regular oval to round. The cytoplasm is moderately abundant and is deeply

basophilic and vacuolated.

ALL-L3

ACUTE LEUKEMIAS

ALL may also be classified on the basis of immunologic markers into: Early pre-B ALL Pre-B ALL B ALL T ALL Null or unclassified ALL (U ALL) - lack B or T markers

and may be the committed lymphoid stem cell)

B CELL MATURATION

T CELL MATURATION

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 leukemias with mixed lineage – occasionally there are acute leukemias that are biphenotypic and display phenotypes for two different lineagesB lymphoid/myeloidT lymphoid/myeloidB/T lymphoidMyeloid/Natural killerA rare trilineage leukemia has also been

seen (was B/T lymphoid/myeloid!)

ACUTE LEUKEMIAS

Acute myeloid leukemia (also called acute granulocytic leukemia) – classification depends uponBone marrow blast morphologyDegree of cell maturationCytochemical stains ImmunophenotypingAML 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

Treatment of leukemias – There are 2 goals:

Eradicate the leukemic cell mass Give supportive care

Except for ALL in children, cures are not common but complete remission (absence of any leukemia related signs and symptoms and return of bone marrow and peripheral blood values to within normal values) is

ACUTE LEUKEMIAS There are four general types of therapy

Chemotherapy – usually a combination of drugs is used Bone marrow transplant Radiotherapy Immunotherapy – stimulate the patients own immune

system to mount a response against the malignant cells

Monoclonal antibodies – examples include Rituxin