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ACUTE & CHRONIC LEUKEMIA
ACUTE LEUKEMIA
BASIC PRINCIPLES
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Neoplastic proliferation of blasts; defined as the accumulation of > 20% blasts in the bone
marrow
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Blasts usually enter the blood stream, resulting in a high WBC count
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Acute leukemia is subdivided into acute lymphoblastic leukemia (ALL) or acute
myelogenous leukemia (AML) based on the phenotype of the blasts
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 TdT is absent in myeloid blasts and mature lymphocytes
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 Usually characterized by lymphoblasts (TdT+) that express CD10, CD19, and CD20
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 Prognosis is based on cytogenetic abnormalities
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t(l2;21) has a good prognosis; more commonly seen in children
ii
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g
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The blasts do not express CD10
 Usually presents in teenagers as a mediastinal (thymic) mass (called acute
lymphoblastic lymphoma because the malignant cells form a mass)

ACUTE MYELOID LEUKEMIA
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Neoplastic accumulation of immature myeloid cells (> 20%) in the bone marrow
Myeloblasts are usually characterized by positive cytoplasmic staining for
myeloperoxidase (MPO)
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Most commonly arises in older adults (average age is 50-60 years)
Sub-classification based on cytogenetic abnormalities, lineage of immature myeloid cells,
and surface markers
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Characterized by t(15;17), which involves translocation of the retinoic acid
receptor (RAR) on chromosome 17 to chromosome 15; RAR disruption blocks
maturation and promyelocytes (blasts) accumulate
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Abnormal promyelocytes contain numerous primary granules that increase the
risk for DIC
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Treatment is with all-trans-retinoic acid (ATRA, a vitamin A derivative), which
binds the altered receptor and causes the blasts to mature (and eventually die)
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Proliferation of monoblasts; usually lack MPO
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 Acute megakaryoblastic leukemia
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Associated with Down syndrome (usually arises before the age of 5)
AML may also arise from pre-existing dysplasia (myelodysplastic syndromes), especially
with prior exposure to alkylating agents or radiotherapy
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 Most patients die from infection or bleeding, though some progress to acute leukemia
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Involvement of lymph nodes leads to generalized lymphadenopathy and is called small
lymphocytic lymphoma
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 Autoimmune hemolytic anemia
 Transformation to diffuse large B-cell lymphoma (Richter transformation)-marked
clinically by an enlarging lymph node or spleen

HAIRY CELL LEUKEMIA
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Neoplastic proliferation of mature B cells characterized by hairy cytoplasmic processes
Cells are positive for tartrate-resistant acid phosphatase (TRAP)
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Lymphadenopathy is usually
absent
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ADULT T-CELL LEUKEMIA/LYMPHOMA (ATLL)
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Neoplastic proliferation of mature CD4+ T cells
Associated with HTLV-1; most commonly seen in Japan and the Caribbean
Clinical features include rash (skin infiltration), generalized lymphadenopathy with
hepatosplenomegaly, and lytic (punched-out) bone lesions with hypercalcemia
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Aggregates of neoplastic cells in the epidermis are called
Pautrier microabscesses
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 Characteristic lymphocytes with cerebriform nuclei (Sezary cells) are seen on blood
smear



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