Chapter 19 Leukaemia Flashcards

1
Q

What is leukemia?

A

A condition where there are tumor cells of hematopoietic origin in the blood and/or bone marrow.

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2
Q

How is leukemia classified in horses?

A

Based on cell of origin (lymphoid or myeloid) and degree of differentiation (acute or chronic).

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3
Q

What are the two main criteria for classifying leukemias?

A

Cell of origin and degree of differentiation.

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4
Q

What characterizes chronic leukemia?

A

A disorder of accumulation where neoplastic cells fail to die, leading to high numbers in peripheral blood.

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5
Q

What characterizes acute leukemia?

A

A disorder of proliferation where neoplastic cells have a growth advantage over normal cells and fail to differentiate completely.

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6
Q

What are the common clinical signs of chronic lymphocytic leukemia (CLL) in horses?

A

Edema of the ventrum, prepuce, and limbs, inappetence, weight loss, fever, poor body condition, mild colic, diarrhea, and lymph node enlargement.

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7
Q

What diagnostic techniques are used for leukemia?

A

Immunophenotyping and cytochemistry.

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8
Q

What is the significance of immunophenotyping in leukemia diagnosis?

A

It determines the cell lineage by identifying specific markers on the cells.

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9
Q

What is the purpose of cytochemistry in leukemia diagnosis?

A

To detect enzyme activity within cells, useful for diagnosing acute myeloid leukemia.

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10
Q

What is the prevalence of chronic leukemia in horses?

A

Quite rare, with few reported cases.

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11
Q

What is a hallmark feature of chronic myeloid leukemia in horses?

A

A marked increase in cell numbers, particularly persistent and unexplained, or evidence of abnormal maturation.

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12
Q

What are the clinical signs of chronic granulocytic leukemia?

A

Lethargy, fever, inflamed and slow-healing skin wounds, severe anemia, and thrombocytopenia.

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13
Q

What is the typical signalment for horses with chronic lymphocytic leukemia?

A

Older horses, usually males, with vague and nonspecific clinical signs.

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14
Q

What is the primary method of diagnosing CLL?

A

Documenting markedly increased numbers of lymphocytes in peripheral blood.

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15
Q

What is the main differential diagnosis for CLL?

A

A leukemic phase of a small cell lymphoma.

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16
Q

What are the clinical outcomes of horses with CLL treated with corticosteroids?

A

Euthanasia after several months due to clinical disease progression or complications like laminitis.

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17
Q

What characterizes acute leukemia in horses?

A

Presence of greater than 20% immature neoplastic cells (blasts) in the bone marrow.

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18
Q

What is the typical age range for horses affected by acute leukemia?

A

2-11 years old.

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19
Q

What are the common clinical signs of acute leukemia?

A

Weight loss, inappetence, fever, edema, lymphadenopathy, depression, diarrhea, colic, and epistaxis.

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20
Q

What is the primary diagnostic clue for leukemia in a hemogram?

A

Bi- or pancytopenia, non-regenerative and persistent, indicating a bone marrow disorder.

21
Q

What is the role of bone marrow aspiration in diagnosing acute leukemia?

A

To confirm the presence of at least 20% blasts, required for diagnosis.

22
Q

What are common biochemical abnormalities in horses with acute leukemia?

A

High total protein due to increased globulins, evidence of liver injury.

23
Q

What is the prognosis for horses with acute leukemia?

A

Uniformly poor, with most horses being euthanized shortly after diagnosis.

24
Q

What treatment has been attempted for horses with acute leukemia?

A

Cytosine arabinoside, prednisolone, but with poor outcomes.

25
Q

What are common findings on necropsy in horses with acute leukemia?

A

Neoplastic cells in bone marrow and extramedullary tissues, tissue necrosis with vascular thrombi.

26
Q

What does a diagnosis of chronic myeloid leukemia indicate in terms of cell lineage?

A

A marked increase in cell numbers and evidence of abnormal maturation or non-responsive cytopenias.

27
Q

What is the prognosis for horses with chronic lymphocytic leukemia?

A

Poor, with many horses being euthanized due to severe disease progression.

28
Q

What is the significance of lymphocyte blastogenesis assays in CLL?

A

They reveal abnormal proliferation of neoplastic B and T cells, indicating dysfunction.

29
Q

What are the main signs of chronic granulocytic leukemia in horses?

A

Severe anemia, thrombocytopenia, leukocytosis with neutrophilia and left shift, monocytosis.

30
Q

What is the main cause of death in horses with acute leukemia?

A

Secondary bacterial infections, complications of sepsis, and spontaneous bleeding due to severe cytopenias.

31
Q

What is the clinical relevance of increased total protein in leukemia cases?

A

Indicates increased globulins, often seen in both acute and chronic leukemia.

32
Q

What is the role of CD markers in immunophenotyping?

A

They help identify the specific lineage of neoplastic cells in leukemia.

33
Q

What is a common treatment approach for leukemia in small animals, but not well-studied in horses?

A

Chemotherapeutic agents, due to unknown efficacy and toxicity in horses.

34
Q

What is a characteristic feature of acute myeloid leukemia (AML) in cytochemistry?

A

Positive staining for myeloid markers such as chloroacetate esterase.

35
Q

What are the signs of chronic myeloid leukemia in bone marrow aspirates?

A

Myeloid hyperplasia with erythroid and megakaryocytic hypoplasia, dysplasia in granulocyte precursors.

36
Q

What are the signs of chronic lymphocytic leukemia in bone marrow aspirates?

A

Low to high numbers of infiltrating lymphocytes, indicating bone marrow involvement.

37
Q

What is the role of monoclonal gammopathy in leukemia diagnosis?

A

Suggests a neoplastic process, often seen in CLL cases.

38
Q

What are the primary clinical signs of leukemia in horses?

A

Vague and nonspecific, including weight loss, fever, edema, and lymphadenopathy.

39
Q

What is the importance of specialized diagnostic techniques for leukemia?

A

To accurately classify and identify the cell lineage of neoplastic cells.

40
Q

What is the significance of ‘blasts’ in leukemia diagnosis?

A

Indicates immature neoplastic cells, essential for diagnosing acute leukemia.

41
Q

What is the role of flow cytometry in leukemia diagnosis?

A

Allows simultaneous application of multiple antibodies to identify cell markers in blood or bone marrow samples.

42
Q

What are common differential diagnoses for lymphocytosis in horses?

A

Epinephrine response, chronic antigenic stimulation, and lymphoma.

43
Q

What is the significance of a left shift in neutrophils for leukemia diagnosis?

A

Indicates a disproportionate presence of immature neutrophils, supporting a diagnosis of chronic myeloid leukemia.

44
Q

What are the typical morphologic features of neoplastic cells in leukemia?

A

Medium to large cells with fine chromatin, sometimes with nucleoli.

45
Q

What are common findings in horses with chronic lymphocytic leukemia?

A

High lymphocyte counts, concurrent cytopenias, inflammatory response, and increased globulins.

46
Q

What is the treatment outcome for horses with leukemia?

A

Generally poor, with many horses being euthanized due to disease progression or complications.

47
Q

What is the role of TLR-4 in the immune response to leukemia?

A

Initiates pathways leading to the activation of NF-kappa B and production of inflammatory mediators.

48
Q

What are the challenges in treating leukemia in horses?

A

Cost, efficacy, and toxicity of drugs used for small animals, along with advanced disease at presentation.