Chapter 19 Leukaemia Flashcards
What is leukemia?
A condition where there are tumor cells of hematopoietic origin in the blood and/or bone marrow.
How is leukemia classified in horses?
Based on cell of origin (lymphoid or myeloid) and degree of differentiation (acute or chronic).
What are the two main criteria for classifying leukemias?
Cell of origin and degree of differentiation.
What characterizes chronic leukemia?
A disorder of accumulation where neoplastic cells fail to die, leading to high numbers in peripheral blood.
What characterizes acute leukemia?
A disorder of proliferation where neoplastic cells have a growth advantage over normal cells and fail to differentiate completely.
What are the common clinical signs of chronic lymphocytic leukemia (CLL) in horses?
Edema of the ventrum, prepuce, and limbs, inappetence, weight loss, fever, poor body condition, mild colic, diarrhea, and lymph node enlargement.
What diagnostic techniques are used for leukemia?
Immunophenotyping and cytochemistry.
What is the significance of immunophenotyping in leukemia diagnosis?
It determines the cell lineage by identifying specific markers on the cells.
What is the purpose of cytochemistry in leukemia diagnosis?
To detect enzyme activity within cells, useful for diagnosing acute myeloid leukemia.
What is the prevalence of chronic leukemia in horses?
Quite rare, with few reported cases.
What is a hallmark feature of chronic myeloid leukemia in horses?
A marked increase in cell numbers, particularly persistent and unexplained, or evidence of abnormal maturation.
What are the clinical signs of chronic granulocytic leukemia?
Lethargy, fever, inflamed and slow-healing skin wounds, severe anemia, and thrombocytopenia.
What is the typical signalment for horses with chronic lymphocytic leukemia?
Older horses, usually males, with vague and nonspecific clinical signs.
What is the primary method of diagnosing CLL?
Documenting markedly increased numbers of lymphocytes in peripheral blood.
What is the main differential diagnosis for CLL?
A leukemic phase of a small cell lymphoma.
What are the clinical outcomes of horses with CLL treated with corticosteroids?
Euthanasia after several months due to clinical disease progression or complications like laminitis.
What characterizes acute leukemia in horses?
Presence of greater than 20% immature neoplastic cells (blasts) in the bone marrow.
What is the typical age range for horses affected by acute leukemia?
2-11 years old.
What are the common clinical signs of acute leukemia?
Weight loss, inappetence, fever, edema, lymphadenopathy, depression, diarrhea, colic, and epistaxis.
What is the primary diagnostic clue for leukemia in a hemogram?
Bi- or pancytopenia, non-regenerative and persistent, indicating a bone marrow disorder.
What is the role of bone marrow aspiration in diagnosing acute leukemia?
To confirm the presence of at least 20% blasts, required for diagnosis.
What are common biochemical abnormalities in horses with acute leukemia?
High total protein due to increased globulins, evidence of liver injury.
What is the prognosis for horses with acute leukemia?
Uniformly poor, with most horses being euthanized shortly after diagnosis.
What treatment has been attempted for horses with acute leukemia?
Cytosine arabinoside, prednisolone, but with poor outcomes.
What are common findings on necropsy in horses with acute leukemia?
Neoplastic cells in bone marrow and extramedullary tissues, tissue necrosis with vascular thrombi.
What does a diagnosis of chronic myeloid leukemia indicate in terms of cell lineage?
A marked increase in cell numbers and evidence of abnormal maturation or non-responsive cytopenias.
What is the prognosis for horses with chronic lymphocytic leukemia?
Poor, with many horses being euthanized due to severe disease progression.
What is the significance of lymphocyte blastogenesis assays in CLL?
They reveal abnormal proliferation of neoplastic B and T cells, indicating dysfunction.
What are the main signs of chronic granulocytic leukemia in horses?
Severe anemia, thrombocytopenia, leukocytosis with neutrophilia and left shift, monocytosis.
What is the main cause of death in horses with acute leukemia?
Secondary bacterial infections, complications of sepsis, and spontaneous bleeding due to severe cytopenias.
What is the clinical relevance of increased total protein in leukemia cases?
Indicates increased globulins, often seen in both acute and chronic leukemia.
What is the role of CD markers in immunophenotyping?
They help identify the specific lineage of neoplastic cells in leukemia.
What is a common treatment approach for leukemia in small animals, but not well-studied in horses?
Chemotherapeutic agents, due to unknown efficacy and toxicity in horses.
What is a characteristic feature of acute myeloid leukemia (AML) in cytochemistry?
Positive staining for myeloid markers such as chloroacetate esterase.
What are the signs of chronic myeloid leukemia in bone marrow aspirates?
Myeloid hyperplasia with erythroid and megakaryocytic hypoplasia, dysplasia in granulocyte precursors.
What are the signs of chronic lymphocytic leukemia in bone marrow aspirates?
Low to high numbers of infiltrating lymphocytes, indicating bone marrow involvement.
What is the role of monoclonal gammopathy in leukemia diagnosis?
Suggests a neoplastic process, often seen in CLL cases.
What are the primary clinical signs of leukemia in horses?
Vague and nonspecific, including weight loss, fever, edema, and lymphadenopathy.
What is the importance of specialized diagnostic techniques for leukemia?
To accurately classify and identify the cell lineage of neoplastic cells.
What is the significance of ‘blasts’ in leukemia diagnosis?
Indicates immature neoplastic cells, essential for diagnosing acute leukemia.
What is the role of flow cytometry in leukemia diagnosis?
Allows simultaneous application of multiple antibodies to identify cell markers in blood or bone marrow samples.
What are common differential diagnoses for lymphocytosis in horses?
Epinephrine response, chronic antigenic stimulation, and lymphoma.
What is the significance of a left shift in neutrophils for leukemia diagnosis?
Indicates a disproportionate presence of immature neutrophils, supporting a diagnosis of chronic myeloid leukemia.
What are the typical morphologic features of neoplastic cells in leukemia?
Medium to large cells with fine chromatin, sometimes with nucleoli.
What are common findings in horses with chronic lymphocytic leukemia?
High lymphocyte counts, concurrent cytopenias, inflammatory response, and increased globulins.
What is the treatment outcome for horses with leukemia?
Generally poor, with many horses being euthanized due to disease progression or complications.
What is the role of TLR-4 in the immune response to leukemia?
Initiates pathways leading to the activation of NF-kappa B and production of inflammatory mediators.
What are the challenges in treating leukemia in horses?
Cost, efficacy, and toxicity of drugs used for small animals, along with advanced disease at presentation.
