Leukemic small cell lymphoma or chronic lymphocytic leukemia in a horse.
Abstract: A 16-year-old, Irish Draft mare was admitted to the referring veterinarian for an annual health check. A mild generalized lymphadenomegaly was noted. Rectal palpation and transrectal ultrasonographic examination revealed prominent mesenteric lymph nodes. A transcutaneous abdominal ultrasonographic evaluation was unremarkable. A CBC revealed a marked leukocytosis (63.06 × 10(3)/μL) and lymphocytosis (58.2 × 10(3)/μL) due to increased numbers of small lymphocytes. No evidence of anemia or thrombocytopenia was found and neutrophil counts were low-normal. Cytologic examination of fine-needle aspirates of multiple lymph nodes and a bone-marrow aspirate revealed the presence of a monomorphic population of small lymphocytes similar to those observed in the peripheral blood, suggesting a leukemic small cell lymphoma (SCL) or chronic lymphocytic leukemia (CLL). As the lymphadenomegaly and peripheral blood lymphocytosis were present simultaneously, the distinction between these 2 conditions was not possible. Immunophenotyping by immunocytochemistry and flow cytometry of the lymphoid cells in peripheral blood determined a T-cell phenotype. As the horse was clinically stable, no treatment was initiated, but regular examinations were undertaken. A CBC repeated 120 days after the diagnosis showed a marked lymphocytosis (157.6 × 10(3)/μL) with no evidence of anemia or other cytopenias. The horse was euthanized 194 days after the initial diagnosis. Histopathology and immunohistochemistry of submandibular lymph nodes and bone marrow confirmed the diagnosis of leukemic SCL or CLL, and a T-cell phenotype. SCL and CLL are rare in horses; previous immunohistochemical studies determined that the T-cell phenotype is predominant. To the authors' knowledge, this is the first report of the combined use of immunocytochemistry and flow cytometry in a horse with leukemic SCL or CLL.
© 2013 American Society for Veterinary Clinical Pathology.
Publication Date: 2013-08-02 PubMed ID: 23909896DOI: 10.1111/vcp.12057Google Scholar: Lookup
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Summary
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The research article discusses the case of an Irish Draft mare with an uncommon lymphoma, chronic lymphocytic leukemia (CLL), or leukemic small cell lymphoma (SCL). This involves the application of immunocytochemistry and flow cytometry for the first time in a horse with the condition.
Case Presentation
- The subject of the study was a 16-year-old Irish Draft mare, which was presented for a routine annual health checkup. The vet noted a mild generalized enlargement of lymph nodes (lymphadenomegaly).
- Subsequent rectal and transrectal ultrasonographic examinations revealed larger than normal mesenteric lymph nodes. On the contrary, the transcutaneous abdominal ultrasound came out normal.
- A Complete Blood Count (CBC) pointed towards a prominent leukocytosis (increased number of white blood cells) and lymphocytosis (increased number of lymphocytes), resulting from an upsurge in small lymphocytes. The neutrophil counts were normal, and no signs of anemia or thrombocytopenia (low platelet count) were observed.
- Cytologic testing of fine-needle aspirates from various lymph nodes and a bone-marrow aspirate revealed a uniform population of small lymphocytes, indicative of SCL or CLL. As the blood lymphocytosis and lymphadenomegaly coexisted, differentiating between the two conditions was not feasible.
Disease Progression and Diagnosis
- Immunophenotyping by immunocytochemistry and flow cytometry was performed on the lymphoid cells in the blood, revealing a T-cell phenotype. No immediate treatment was initiated since the horse was clinically stable, but regular examinations were undertaken.
- A repeat CBC after 120 days from the initial diagnosis showed a further increase in lymphocytes, while other parameters remained unchanged. Unfortunately, the horse was euthanized 194 days after the initial diagnosis.
- Postmortem histopathology and immunohisochemistry affirmed the prior diagnosis of SCL or CLL, and a T-cell phenotype. The study reiterated that both SCL and CLL are rather infrequent occurrences in horses; earlier immunohistochemical studies have established the predominance of the T-cell phenotype.
Contribution to Veterinary Oncology
- This case is extraordinary because it’s the first to report using combined immunocytochemistry and flow cytometry in a horse diagnosed with SCL or CLL. This may pave the way for future research and advancements in the management and diagnosis of equine lymphoma and leukemia.
Cite This Article
APA
Cian F, Tyner G, Martini V, Comazzi S, Archer J.
(2013).
Leukemic small cell lymphoma or chronic lymphocytic leukemia in a horse.
Vet Clin Pathol, 42(3), 301-306.
https://doi.org/10.1111/vcp.12057 Publication
Researcher Affiliations
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK.
MeSH Terms
- Animals
- Biopsy, Fine-Needle / veterinary
- Bone Marrow / pathology
- Diagnosis, Differential
- Female
- Flow Cytometry / veterinary
- Horse Diseases / genetics
- Horse Diseases / pathology
- Horses
- Immunohistochemistry / veterinary
- Immunophenotyping / veterinary
- Leukemia, Lymphocytic, Chronic, B-Cell / genetics
- Leukemia, Lymphocytic, Chronic, B-Cell / pathology
- Leukemia, Lymphocytic, Chronic, B-Cell / veterinary
- Lymphocytes / pathology
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