Understanding Acute Myeloid Leukemia (AML): Classification, Subtypes, and Hematological Features

 

Acute Myeloid Leukemia (AML)

Acute Myeloid Leukemia (AML) is a rapidly progressing cancer that affects the blood and bone marrow, characterized by the rapid growth of abnormal myeloid cells.

OR
Acute Myeloid Leukemia (AML) is a type of blood cancer. In children, it occurs in about 2 to 3 out of every 100,000 children per year.In older adults, particularly those over 60 years old, the incidence rises significantly to around 15 cases per 100,000 people per year.

WHO Classification (Newer):

Incorporates and interrelates morphology (cell appearance), cytogenetics (chromosomal abnormalities), molecular genetics (genetic mutations), and immunologic markers (cell surface proteins).

Allows for a more comprehensive understanding of leukemia subtypes by considering multiple factors.

Defines acute leukemia as having 20% or more blasts (immature cells) in the blood and bone marrow.

FAB Classification (Older):

Primarily based on morphological features observed under the microscope.

Classifies leukemia subtypes based on the degree of differentiation along different cell lines and the extent of cell maturation.

Defines acute leukemia as having 30% or more blasts in the blood and bone marrow.

 

AML-M0

AML-M1

AML-M2

AML-M3

-Absence of visible granules in blast cytoplasm.

-Negative cytochemical stain reactions.

-Positive for myeloid markers: CD13, CD33.

- Common in adults and infants under 1 year.

- May exhibit leucocytosis.

- Lack of cellular maturation.

- Predominance of poorly differentiated myeloblasts in peripheral blood.

- Possible presence of vacuoles.

- Decreased platelet count.

- Scanty azurophilic granules or Auer rods may be present.

 

- Presence of more differentiated cells in bone marrow.

- Common in adults.

- Leucocytosis in 50% of cases.

- Thrombocytopenia.

- Predominance of myeloblasts in peripheral blood.

- Hypercellular bone marrow.

- Variable presence of azurophilic granules and Auer rods.

 

- Seen in young adults.

- Rapid progression, may cause DIC.

- Predominance of promyelocytes.

- Delicate nucleus with foldings.

- Common clinical finding: bleeding.

- Presence of Faggot cells - cells with multiple Auer rods

 

AML-M4

AML-M5

AML-M5a

AML-M5b

- Presence of myelocytic and monocytic cells.

- Extramedullary infiltration common.

- Elevated muramidase levels.

- Anemia and thrombocytopenia.

- Cytochemical stains reveal two cell populations.

 

- Common in adults and infants under 1 year.

- May exhibit leucocytosis.

- Lack of cellular maturation.

- Predominance of poorly differentiated myeloblasts in peripheral blood.

- Possible presence of vacuoles.

- Decreased platelet count.

- Scanty azurophilic granules or Auer rods may be present.

 

- Poorly differentiated.

- Monoblasts predominate.

- Presence of azurophilic granules.

 

- Well differentiated.

- Majority of monocytic cells.

- Blast percentage less than 30%.

- Fine azurophilic granules present.

 



AML-M6

AML-M7

- Predominance of erythroblasts.

- Characterized by anemia with poikilocytosis and anisocytosis.

- Diagnosis if more than 50% of bone marrow cells are erythroid and 30% are blast.

- True erythroleukemia if bone marrow is replaced by proliferating normoblasts.

 

- Peripheral blood pancytopenia.

- High peripheral blood blast count.

- Micro megakaryocytes and undifferentiated blasts.

- Increased fibroblasts in bone marrow.

- Cytoplasmic budding observed.

 








Peripheral Blood AML

·         Anemia (Normocytic Normochromic)

·         Thrombocytopenia

·         Leukocytosis

·         Platelet Abnormalities

·         Neutropenia with Morphologic Abnormalities

·         Blasts as Predominant Cells

BM CHANGES IN AML

·         Hypercellularity

·         Predominance of Myeloblasts

·         Presence of Immature Granulocytes

·         Increased Erythroblasts

·         Modest Increase in Plasma Cells

·         Presence of Monocytes

·         Megaloblastic Erythroblasts

·         Presence of Ring Sideroblasts

·         Scanty Erythropoietic Cells

·         Reduction in Megakaryocytes

·         Myelofibrosis

Blast Classification in Acute Myeloid Leukemia (AML):

Type 1: Characterized by typical myeloblast morphology featuring open chromatin and prominent nucleoli.

Displays immature deep blue cytoplasm lacking granules.

Type 2: Resembles Type 1 but additionally exhibits up to 20 discrete azurophilic granules within the cytoplasm.

Type 3: Shares similarities with Type 1 but showcases a notable presence of numerous azurophilic granules within the cytoplasm.


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https://pathologistfromkust.blogspot.com/2024/03/understanding-white-blood-cell.html


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