Lecture 6 Acute Myeloid Leukemias

Question 1

Why do you find a Leukoerythroblastic picture in acute leukemias?

Answer 1

A leukoerythroblastic picture occurs in acute leukemia because the marrow gets filled with blast cells and so that marrow pushes out immature red cells, like NRBC, etc.

Question 2

How does the % of blasts in the marrow and PB compare between chronic and acute leukemia?

Answer 2

Chronic: < 5% in PB and < 30% in BM.
Acute: > 5% in PB and > 30% in BM.

Question 3

What is the definition of Acute Myelogenous Leukemia (AML)?

Answer 3

AML: Defined as a malignant disease of hematopoietic tissue characterized by replacement of normal bone marrow elements with abnormal (neoplastic) blood cells.

Question 4

What is the probably cause of Acute Myeloproliferative Leukemia?

Answer 4

Probably a stem cell defect.

Question 5

What is the prognosis for AML if left untreated?

Answer 5

AML is rapidly fatal if untreated. Death due to pancytopenia such as anemia, bleeding and infection.

Question 6

What are causes of AML?

Answer 6

1. Radiation
2. Chemical and Drugs - e.g. benzene, chemotherapy drugs (alkylating agents)
3. Viruses - association (not proven) with Human T-Cell Leukemia Lymphoma (HTLL-1), HTLV-II, and Epstein -Barr virus
4. Genetics –> unaffected twin at greater risk
5. People with chromosomal abnormalities are at greater risk.

Question 7

What are important morphological criteria to compare when distinguishing between lymphocytic or myeloblastic?

Answer 7

Morphologic Features to Compare:
1. Size of Cell (Large in AML Myeloblast, Small in ALL Lymphoblast)
2. Nucleus to cytoplasmic ratio (Moderate in AML, Scant in ALL)
3. Shape of nuclear outline
4. Number of Nucleoli (Prominent in AML, Indistinct <2 in ALL)
5. Degree of cytoplasmic maturation
6. Presence of Auer Rods (Present in 50-60% in AML, never present in ALL)
7. Chromatin Pattern

Question 8

How many dysmyelopoiesis abnormalities can you name associated with AML?

Answer 8

Dysmyelopoiesis abnormalities:
- Nuclear / cytoplasmic asynchrony
- Leukemic hiatus
- Nuclear abnormalities
- Pseudo-Pelger-Huet changes
- Hypersegnentation
- Unusual nuclear projections
- Granule abnormalities (increased size & #, decreased # or 0, auer rods)
- Loss of cellular organelles
- Irregular cytoplasmic basophilia

Question 9

How many dyserythropoiesis abnormalities can you name associated with AML?

Answer 9

Gigantism
Multinuclearity
Nuclear lobulation
Nuclear fragments
Pyknosis
Megaloblastoid changes (more solid)
Cytoplasmic vacuoles

Question 10

How many dysmegakaryocytopoiesis abnormalities can you name associated with AML?

Answer 10

Giant platelets (megathrombocytes)
Hypernuclear and hyponuclear lobulation
Micromegakaryocytes
Granule abnormalities (Giant granules, abnormal granules)

Question 11

What are the 5 main cytochemical stains?

Answer 11

1. Myeloperoxidase
2. Sudan Black B
3. Specific Esterase (Napthol AS-D Chloroacetate)
4. Non-specific Esterase
5. Periodic Acid Schiff

Question 12

What is myeloperoxidase used for as a cytochemical stain?

Answer 12

Used to differentiate Acute Myelogenous Leukemia (AML) from Acute Lymphocytic Leukemia (ALL). Peroxidase is present in primary granules of myeloid cells. Monocytes most often weak positive. More specific than Sudan Black B.

Peroxidase enzyme is labile so fresh specimens should be used.

Question 13

What is Sudan Black B used for?

Answer 13

Sudan Black B stains phospholipids in primary and secondary granules of myeloid cells. Monocytic lysozomal granules stain weaker. Differentiates AML form ALL.

Reactivity does not diminish with storage therefore very useful for specimens that are not fresh.

Most sensitive stain for granulocytes and their precursors. Rare cases of ALL positive.

Question 14

What is Specific Esterase (Napthol AS-D Chloroacetate) used for?

Answer 14

Sensitive for esterase enzyme present in cytoplasm of neutrophils, basophils and mast cells. Negative in eosinophils and monocytes. Not as sensitive as peroxidase. This stain used for myeloid differentiation of paraffin-embedded tissue section.

Question 15

What are non-specific esterase’s used for? (Such as Alpha-Naphthyl Acetate or Alpha-Napthyl Butyrate)

Answer 15

Positive for Monocytes, negative in myeloid cells therefore useful to confirm Acute Monocytic Leukemia.

Question 16

What cytochemical stain is used in conjunction with sodium fluoride to differentiate myeloid cells from X?

Answer 16

When you add sodium fluoride to Napthol AS-D Acetate (NASDA) it renders the monocytes negative but shows the granulocytes thus helping to differentiate myeloid cells which remain positive. (NASDA is specific for both granulocytes and monocytes).

Question 17

How is periodic acid schiff used as a cytochemical stain in hematology?

Answer 17

As it stains glycogen, glycolipids, glycoprotein, and polysaccharides in stains lymphocytes, myeloid cells, monocytes and megakaryocytes and therefore not helpful there but it is most helpful if there is a Acute Erythroleukemia (M6) as it has a strong PAS activity.

Question 18

How does immunological flow cytometry help diagnosis leukemias?

Answer 18

Uses monoclonal antibodies to attach to specific antigens of myeloid and lymphoid origin - then reaction measured by use of Flow Cytometry.

Commonly used test - replaced cytochemistry techniques.

Flow cytometry is most helpful for detecting undifferentiated (very immature) cells, mixed lineage (both lymphoid and myeloid) and megakayrocytic (M7) leukemia where morphological and cytochemical stains cannot identify abnormal cells.

Question 19

How does flow cytometry affect treatment protocols?

Answer 19

Some treatment protocols are based on immunologic markers more than cytochemical reaction to determine treatment and patient outcome.

Question 20

How is molecular diagnostics used for to diagnose leukemias?

Answer 20

Uses DNA, RNA, Nucleic acid sequences to identify abnormalities associated with diseases.

Question 21

How is electron microscopic studies used to diagnose leukemias?

Answer 21

Helpful to identify specific granules that cannot be identified with Romanowsky stain, special stains and light microscopy. (ie. M0 rare granules, M1 few granules).

Question 22

What is a type I blast cell as per FAB?

Answer 22

Type I:
1. No cytoplasmic differentiation (maturation) therefore no granules.
2. Prominent nucleoli and fine chromatin pattern are important characteristics.
3. Smaller blasts with high nucleus to cytoplasm ratio (small amount of cytoplasm).

Question 23

What type of blast cell per FAB has more than 20 granules?

Answer 23

Type III: More than 20 granules with lower nucleus to cytoplasm than Type I. Generally centrally located nucelus.

Question 24

What is a type II blast cell as per FAB?

Answer 24

Type II: Fine azurophilic granules <20, suggesting minimal differentiation. Nucleus to Cytoplasm ratio is lower than in Type I (more cytoplasm). Generally centrally located nucleus.

Question 25

What are auer bodies?

Answer 25

Auer bodies are cytoplasmic inclusions representing an agglomeration of azurophilic (primary) granules, i.e. it is a fusion of primary granules.

They form rod-like bundles 0.2 to 5 um in length.

Question 26

What are faggot cells?

Answer 26

Cells with multiple auer bodies lumped together.

Question 27

How does a Type III Blast differs from a Promyelocyte?

Answer 27

1. Chromatin begins to condense in the promyelocyte.
2. Size of the promyelocyte is bigger than the blast.
3. Blast has a higher nucleus to cytoplasm ratio.
4. Promyelocytes have
   a) primary granules that are dark blue or dark reddish-blue that overlap the nucleus.
   b) Golgi apparatus may show has clear area around nucleus.

Question 28

What enzyme and other stuff does auer rods have in them?

Answer 28

Auer rods contain peroxidase (lots), lysosomal enzymes and large crystalline inclusions.

Question 29

What are the stains Sudan Black B and Myeloperoxidase useful for?

Answer 29

MPO and SBB are useful for differentiating AML from ALL but SBB can be used on specimens that are not fresh.

Question 30

What is specific esterase (Naphthol AS-D Chloroacetate) useful for?

Answer 30

Specific Esterase (Naphthol AS-D Chloroacetate), parallels results of SBB and MPO is used to separate myeloid differentiation of paraffin-embedded tissue sections.

Question 31

What stains can be used to confirm Acute Monocytic Leukemia and Acute Megakaryoblastic Leukemia?

Answer 31

Non-Specific Esterases useful for confirming Acute Monocytic Leukemia and Acute Megakaryoblastic Leukemia.

Question 32

What condition can PAS be helpful to support the diagnosis of?

Answer 32

PAS is most helpful to support the diagnosis of Acute Erythroleukemia as strong PAS positivity is usually present.