Histopathology of Leukemia

Types of Leukemia

• There are 4 main type of leukemia

– Acute Lymphoblastic Leukemia (ALL):• This is the most common type of leukemia in young children. ALL can also occurs in

adults.

– Acute Myelogenous Leukemia (AML):• AML is a common type of leukemia. It occurs in children and adults. AML is the

most common type of acute leukemia in adults.– Chronic Lymphocytic Leukemia (CLL):

• The most common chronic leukemia in middle aged adults; rarely occurs in children.

– Chronic Myelogenous Leukemia (CML):• This type of leukemia mainly afects adults. A person with CML may have few or no

symptoms for months or years before entering a phase in which leukemia cells grow more rapidly.

Types of Leukemia (cont’d)

• Rare type of leukemia:– Hairy cell leukemia:

• A rare, slow growing cancer of the blood– Myelodysplastic syndrome:

• A type of cancer in which the bone marrow doen no make enough healthy blood cells and there are abnormal (blastic) cells in the blood and/or bone marrow

– Myeloproliferative disorders:• A group of conditions that cause blood cells (platelets,

WBCs, and RBCs) to grow abnormally in the bone marrow

Acute Lymphoblastic Leukemia (ALL)

• Composed of immature precursor B- (pre B) or T-lymphocytes (pre T)

• 85% of ALL are precursor B cell, precursor T cell ALL are infrequent

• Common malignancy under 15years; peak age 2-5 years

• Risk Factors: Trisomy 21, Ataxia-Telangectasia, Bloom Syndrome

• Lab investigation: – Anemia, neutropenia and

thrombocytopenia– Total WBC count elevated– Platelet count decreased– Hb: decreased– Peripheral smear: circulating leukemic

blast cells

Chronic Lymphocytic Leukemia (CLL)

• Increased Peripheral blood lymphocytosis

• Most common type of leukemia in Western world

• Risk progressively increases with age (>60 years)

• More common in Males• Lab Investigation:

– Anemia: Very late in disease– Total WBC count: Markedly

Elevated (100,000/mm3)– Peripheral blood smear:

Lymphocytosis, “Smudge cells” (arrows)

Acute Myelogenous Leukemia (AML)

• Proliferation of blast cells, mainly in the marrow

• Incidence: Adults (80%), Children (15-20%)

• Lab Investigations:– Total WBC count: Increase,

sometimes normal or decreased– Anemia– Thrombocytopenia– Peripheral blood smear:

presence of atypical myeloid cells, circulating “blasts”

– Bone Marrow: >20% blastsAuer Rods (arrows)

Chronic Myelogenous Leukemia (CML)

• Incidence: Adults (25-60 years)• Presence of a distinctive molecular abnormality• Philadelphia chromosome (9:22)• Inhibition of apoptosis and increase in cell

division• Lab Investigation:

– Total WBC: >100,000/mm3

– Platelet count: Increased initially, later thrombocytopenia

– Peripheral blood smear: • Myeloid series in all stages of development• Eosinophils & basophils• Very low ALP activity (high in reactive leukocytes)

– Bone Marrow:• Hypercellularity• Myeloid & megakaryocytic lineage• Eosinophils & basophils increase• Myeloblasts are <5%• Later stages show collage proliferation

Diagnostic tests– Medical history and physical examination– Complete blood count– Blood chemistry tests– Bleeding and clotting factors– Cytochemistry– Flow cytometry– Immunohistochemistry– Cytogenetics– Fluorescent in situ hybridization (FISH)– Polymerase chain reaction– Bone marrow aspiration and biopsy– Lumbar puncture– Lymph node biopsy

Hairy Cell Leukemia