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Questions and Answers
What is a key feature of eosinophilic lymphadenitis?
What is a key feature of eosinophilic lymphadenitis?
Which condition is most commonly associated with mixed cell lymphadenitis?
Which condition is most commonly associated with mixed cell lymphadenitis?
What characterizes lymphoma based on the lymphocyte population?
What characterizes lymphoma based on the lymphocyte population?
What is a potential cause of pyogranulomatous lymphadenitis?
What is a potential cause of pyogranulomatous lymphadenitis?
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In lymphomas, which immunophenotype classification yields important treatment implications?
In lymphomas, which immunophenotype classification yields important treatment implications?
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What is the primary purpose of staging in relation to lymphadenomegaly?
What is the primary purpose of staging in relation to lymphadenomegaly?
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Which of the following lymph nodes is located near the ventral angle of the jaw?
Which of the following lymph nodes is located near the ventral angle of the jaw?
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What is one of the recommended methods for making a diagnostic smear?
What is one of the recommended methods for making a diagnostic smear?
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Which process is NOT recommended to enhance diagnostic ability when creating smears?
Which process is NOT recommended to enhance diagnostic ability when creating smears?
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Which lymph node is responsible for draining the area distal to the stifle?
Which lymph node is responsible for draining the area distal to the stifle?
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What is a key factor in evaluating lymph node samples?
What is a key factor in evaluating lymph node samples?
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Which technique improves the dispersion of cells in diagnostic smears?
Which technique improves the dispersion of cells in diagnostic smears?
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The prescapular lymph nodes primarily drain which area?
The prescapular lymph nodes primarily drain which area?
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What factor differentiates absolute erythrocytosis from relative erythrocytosis?
What factor differentiates absolute erythrocytosis from relative erythrocytosis?
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Which condition is associated with increased Erythropoietin levels in erythrocytosis?
Which condition is associated with increased Erythropoietin levels in erythrocytosis?
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What is a common cause of relative erythrocytosis?
What is a common cause of relative erythrocytosis?
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Which option describes appropriate erythrocytosis?
Which option describes appropriate erythrocytosis?
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What does splenic contraction cause in animals?
What does splenic contraction cause in animals?
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Which condition is considered a primary cause of erythrocytosis?
Which condition is considered a primary cause of erythrocytosis?
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In which scenario would you find a normal Erythropoietin level?
In which scenario would you find a normal Erythropoietin level?
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Which factor is NOT associated with absolute erythrocytosis?
Which factor is NOT associated with absolute erythrocytosis?
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What is the primary hormonal regulator of RBC production?
What is the primary hormonal regulator of RBC production?
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Which condition is primarily associated with an absolute increase in RBC mass?
Which condition is primarily associated with an absolute increase in RBC mass?
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What causes erythropoietin production to be upregulated?
What causes erythropoietin production to be upregulated?
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What is the primary effect of increased blood viscosity due to erythrocytosis?
What is the primary effect of increased blood viscosity due to erythrocytosis?
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Which of the following breeds is known to have a naturally higher RBC mass?
Which of the following breeds is known to have a naturally higher RBC mass?
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Which factor is NOT associated with relative erythrocytosis?
Which factor is NOT associated with relative erythrocytosis?
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Which finding is most indicative of relative erythrocytosis due to dehydration?
Which finding is most indicative of relative erythrocytosis due to dehydration?
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What was identified on the abdominal ultrasound in Sally's case?
What was identified on the abdominal ultrasound in Sally's case?
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What physiological response can lead to transient erythrocytosis in animals?
What physiological response can lead to transient erythrocytosis in animals?
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What defines absolute erythrocytosis?
What defines absolute erythrocytosis?
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Which of the following scenarios would most likely induce inappropriate erythropoietin production?
Which of the following scenarios would most likely induce inappropriate erythropoietin production?
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What was the finding of the cytology from the fine needle aspiration of the renal mass?
What was the finding of the cytology from the fine needle aspiration of the renal mass?
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The term 'polycythemia' is most strictly used to refer to:
The term 'polycythemia' is most strictly used to refer to:
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Which condition is NOT a cause of secondary absolute erythrocytosis?
Which condition is NOT a cause of secondary absolute erythrocytosis?
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What was Sally's packed cell volume (PCV) two weeks post-operation?
What was Sally's packed cell volume (PCV) two weeks post-operation?
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In which situation would lymph node aspiration generally be indicated?
In which situation would lymph node aspiration generally be indicated?
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What condition can cause a redistribution of red blood cells from the spleen?
What condition can cause a redistribution of red blood cells from the spleen?
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Which of the following is NOT a differential for an enlarged lymph node?
Which of the following is NOT a differential for an enlarged lymph node?
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What characterizes absolute erythrocytosis?
What characterizes absolute erythrocytosis?
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Which option represents a secondary cause of erythrocytosis?
Which option represents a secondary cause of erythrocytosis?
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What type of erythrocytosis occurs when EPO is normal or decreased?
What type of erythrocytosis occurs when EPO is normal or decreased?
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During an epinephrine response, which mechanism accounts for increased RBC counts?
During an epinephrine response, which mechanism accounts for increased RBC counts?
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Inappropriate secondary erythrocytosis is characterized by what?
Inappropriate secondary erythrocytosis is characterized by what?
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What lab finding could indicate dehydration as a cause of relative erythrocytosis?
What lab finding could indicate dehydration as a cause of relative erythrocytosis?
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Which of the following is considered an appropriate cause of secondary erythrocytosis?
Which of the following is considered an appropriate cause of secondary erythrocytosis?
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Which of the following conditions would most likely result in compensatory erythrocytosis?
Which of the following conditions would most likely result in compensatory erythrocytosis?
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Which of the following best describes polycythemia vera?
Which of the following best describes polycythemia vera?
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What change in laboratory results might be expected in absolute erythrocytosis?
What change in laboratory results might be expected in absolute erythrocytosis?
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Study Notes
Erythrocytosis and Polycythemia
- Erythrocytosis is an increase in red blood cell (RBC) mass, often measured by hematocrit (HCT/PCV), RBC count, and/or hemoglobin (Hgb).
- Polycythemia means "many cells in the blood." Most pathologists reserve "polycythemia" for neoplastic conditions affecting RBC production (polycythemia vera), which is a neoplastic proliferation of RBCs.
- Others use the terms interchangeably, creating confusion.
Learning Objectives
- Appreciate breed-specific differences in RBC mass.
- Identify the primary hormonal regulator of RBC production, where it's produced, and what stimulates it.
- Understand the underlying causes of erythrocytosis and their mechanisms.
Why Isn't More Blood Better?
- Increased blood viscosity leads to RBC sludging in vessels, impairing blood flow.
- Impaired blood flow decreases tissue oxygenation.
- Possible consequences: congested mucous membranes, dilated retinal vessels, and seizures.
Breed Specific Differences
- Some breeds (e.g., sighthounds, greyhounds, certain dachshunds, racing horses, warm-blooded breeds) have naturally higher RBC masses.
RBC Production - About EPO
- Erythropoietin (EPO) is the primary hormonal regulator of RBC production.
- EPO is produced by the fetal liver and the adult kidney.
- EPO production is stimulated by renal hypoxia, not directly by RBC mass.
- Anemia, poor renal perfusion, and poor oxygenation of the blood also trigger increased EPO production.
Relative Erythrocytosis
- Not a true increase in RBC mass.
- Results from factors like dehydration (reduced plasma volume, hemoconcentration), splenic contraction (redistribution of RBCs from the spleen).
- Certain animals (cats, horses) are more excitable, making splenic contraction a more important consideration.
Relative Erythrocytosis: Dehydration
- Most common cause of mild to moderate erythrocytosis in veterinary medicine.
- Associated with a decrease in plasma volume rather than an increase in RBC mass.
- Clinical signs often include: dry or tacky mucous membranes, tenting of the skin.
- Laboratory findings might include increased protein (total protein, albumin), highly concentrated urine (high USG), and increased urea/creatinine (pre-renal azotemia).
- Treatment involves rehydration and reevaluation.
Relative Erythrocytosis: Splenic Contraction
- RBCs have shifted from the spleen into the bloodstream.
- Associated with excitement, fear, or exercise.
- More frequent in cats and horses than dogs.
- Animals have larger splenic RBC reserves.
- May also see an increase in lymphocytes. (epinephrine induced).
Absolute Erythrocytosis
- Refers to a true increase in RBC mass.
- Rule out causes of relative erythrocytosis.
- Primary is rare, EPO-independent, and caused by polycythemia vera (neoplastic proliferation of mature RBCs independent of EPO).
Absolute Erythrocytosis - Secondary
- EPO-dependent (increased EPO).
- Appropriate response to hypoxia/hypoxemia (e.g., heart disease, lung disease, high altitudes).
- Inappropriate response when no systemic hypoxia/hypoxemia exists (e.g., renal lesions, tumors or EPO or EPO-like substances or doping).
Summary of Classification
- A table summarizes the key factors and findings correlated with relative and absolute erythrocytosis.
Case Example: Sally
- A 7-year-old spayed female mixed-breed dog with anorexia and lethargy showed various abnormal blood test results.
- Further diagnostics (thoracic radiographs to rule out heart or lung disease, abdominal ultrasound for kidney abnormalities), and blood tests led to a diagnosis.
- Diagnosis was confirmed by fine needle aspiration of the mass. Sally's mass was determined to be atypical sarcoma; which was the source of increased EPO.
- Post-surgical recovery was positive.
Lymph Node Cytology - Learning Objectives
- Understand how lymphocytes size relative to other blood cells.
- Understand the normal cellular composition of a lymph node.
- Identify common cell types in lymph nodes.
- Diagnose an enlarged lymph node via cytology, understanding differences in cellular composition.
When to Aspirate a Lymph Node
- Lymphadenomegaly or enlargement of one or more lymph nodes.
- Detected by palpation, radiography, or ultrasonography.
- Evaluate for metastasis.
Commonly Sampled Lymph Nodes
- A table categorizes locations and the areas drained by sampled lymph nodes.
Making a Diagnostic Smear
- Goal is creating a thin layer of intact cells on a rapidly air-dried slide.
- Methods for making smears include impression smears, fine-needle aspiration technique, and fine-needle non-aspiration technique.
- Proper "squashing" techniques improve cell dispersion.
Sample Evaluation
- Evaluates cellularity, cell types, morphology, and relative proportions of each type to determine if the sample is from a lymph node.
- Additional structures, such as salivary epithelium, adipose tissue, and muscle can be differentiated from lymph nodes.
Sizing of Lymphocytes & Cytomorphology
- Differentiates small, intermediate, and large lymphocytes based on morphological characteristics.
Normal Lymph Node
- 90% small lymphocytes, 10% intermediate and large lymphocytes are typically found.
- Other cells, including macrophages, plasma cells, mast cells, are less numerous.
- Lysed cells and lymphoglandular bodies can also be seen.
Differential Diagnoses for Enlarged Lymph Nodes
- Reactive (hyperplastic) lymph node.
- Inflammatory (lymphadenitis)
- Neoplastic (lymphoma).
- Metastatic neoplastic process from other sites.
Reactive Lymph Node
- Caused by antigenic response to inflammation, infection, immune-mediated disease or neoplasia
- Characterized by predominance of small lymphocytes (>75%), increased numbers of intermediate & large lymphocytes (up to 25%).
- Increased plasma cells are seen in variable numbers, along with Mott cells (plasma cells filled with immunoglobulin-containing vacuoles -- also called Russell bodies). Neutrophils might be present.
Lymphadenitis
- Inflammation of a lymph node.
- Many etiologies (neutrophilic, eosinophilic, mixed).
- Be cautious about blood contamination in the sample.
- Characterized by the predominant type of inflammatory cell.
Neutrophilic Lymphadenitis
- Purulent/suppurative lymphadenitis.
-
5% neutrophils present. (Must rule out other causes of neutrophils like blood contamination).
- Non-specific; might be related to bacterial, neoplastic conditions, or immune-mediated disease.
- Dental disease might be a cause in mandibular lymph nodes.
(Pyo)Granulomatous Lymphadenitis
- Macrophagic or histiocytic lymphadenitis.
- Increased macrophages
- Increased neutrophils and macrophages.
- Often related to chronic inflammation from bacteria (e.g., filamentous, acid-fast), fungi (yeast/hyphae).
Eosinophilic Lymphadenitis
-
3% eosinophils.
- Multiple causes: allergies, hypersensitivity, local skin disease (e.g., atopic dermatitis), parasites, fungal infections (e.g., Pythium), paraneoplastic conditions (e.g., lymphoma, MCT).
Mixed Cell Lymphadenitis
- Most common type of inflammatory lymphadenitis.
- Non-specific findings.
- Due to a combination of factors.
Lymphoma
- Predominance (>50%) of monomorphic lymphocyte population.
- Often characterized by large lymphocytes with atypia (e.g., open chromatin, prominent nucleoli).
- Potential for a small cell, well-differentiated variant requiring additional tests (e.g., flow cytometry, PARR).
- Further testing of immunophenotype (B or T cells) is important to determine prognosis and treatment.
Metastatic Neoplasia
- Foreign cell population presence.
- Common sources include epithelial cells (carcinoma), round cell origin (lymphoma, etc), or other tumor types metastasizing to lymph nodes (e.g., melanoma, neuroendocrine tumors, sarcomas; less common).
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Description
Test your knowledge on lymphadenitis and lymphoma in veterinary medicine. This quiz covers key features, classification, diagnosis, and lymph node functions. Perfect for veterinary students or professionals looking to assess their understanding of lymphatic conditions.
