Extreme lymphocytosis with myelomonocytic morphology in a horse with diffuse large B-cell lymphoma.
Abstract: An 11-year-old, 443-kg Haflinger mare was presented to the North Carolina State University Veterinary Teaching Hospital with a 2-week history of lethargy and a 3-day duration of anorexia, pyrexia, tachycardia, and ventral edema. Severe pitting edema, peripheral lymphadenopathy, and a caudal abdominal mass were noted on physical examination. An extreme leukocytosis (154.3 × 103 /μL) and microscopic hematologic findings suggestive of myelomonocytic leukemia were observed. Serum protein electrophoresis revealed a monoclonal gammopathy and urine protein electrophoresis revealed a monoclonal light chain proteinuria. Necropsy and histopathology confirmed widespread neoplastic infiltration in many organs with a heterogenous population of cells; there was no apparent evidence of bone marrow involvement. Immunohistochemistry confirmed presence of a majority of B cells with a limited antigen expression, admixed with a lower number of T cells. Molecular clonality analysis of IgH2, IgH3, and kappa-deleting element (KDE, B cell) on whole blood and KDE on infiltrated tissues revealed clonal rearrangements, and the KDE intron clones that amplified in blood and in infiltrated tissue were identical. In contrast, the clonality analysis of T-cell receptor γ revealed no clonality on blood cells and infiltrated tissues. In conjunction with the histopathologic changes, the lesion was interpreted to be composed of neoplastic B cells with a reactive T-cell population. Polymerase chain reaction testing for equine herpes virus 5 was negative. The final diagnosis was diffuse large B-cell lymphoma with a marked hematogenous component.
© 2016 American Society for Veterinary Clinical Pathology.
Publication Date: 2016-12-21 PubMed ID: 28001311DOI: 10.1111/vcp.12435Google Scholar: Lookup
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Summary
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The research describes the medical condition of an 11-year-old Haflinger mare, diagnosed with diffuse large B-cell lymphoma, characterised by extreme lymphocytosis with myelomonocytic morphology.
Presentation and Initial Diagnosis
- The horse was brought to the North Carolina State University Veterinary Teaching Hospital following two weeks of lethargy and three days of anorexia, high body temperature, increased heart rate, and swelling in the lower body.
- Physical examinations revealed severe edema, swelling of the peripheral lymph nodes, and a mass in the lower abdomen.
- Blood tests indicated an extreme white blood cell count and microscopic hematologic findings resembled myelomonocytic leukemia – a type of cancer affecting white blood cells.
- Tests of the serum and urine showed abnormally high levels of specific proteins, suggesting a monoclonal gammopathy and monoclonal light chain proteinuria, both conditions usually related to multiple myeloma – a cancer of plasma cells.
Post-Mortem Findings and Final Diagnosis
- A necropsy and subsequent histopathological examination confirmed the presence of widespread cancerous cells in many organs, but no apparent involvement of the bone marrow.
- Immunohistochemistry, a test that detects antibodies in tissue, found a majority of the cells to be B cells, with a low number of T cells. B cells and T cells are two types of white blood cells.
- Genetic testing on the blood and infiltrated tissues identified identical clonal rearrangements – changes that occur when cells duplicate – in the B cells, pointing to a cancerous condition. However, the T cells did not show such changes, suggesting their reactivity to the B cell malignancy.
- Tests for equine herpes virus 5 were conducted due to its known association with certain cases of lymphoma in horses. These came back negative.
- Based on the combined clinical, hematological, histopathological, and molecular findings, the horse was diagnosed with diffuse large B-cell lymphoma with a significant hematogenous component – indicating that the cancer had spread through the bloodstream.
Cite This Article
APA
Meichner K, Kraszeski BH, Durrant JR, Grindem CB, Breuhaus BA, Moore PF, Neel JA, Linder KE, Borst LB, Fogle JE, Tarigo JL.
(2016).
Extreme lymphocytosis with myelomonocytic morphology in a horse with diffuse large B-cell lymphoma.
Vet Clin Pathol, 46(1), 64-71.
https://doi.org/10.1111/vcp.12435 Publication
Researcher Affiliations
- Department of Pathology, University of Georgia College of Veterinary Medicine, Athens, GA, USA.
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
- Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
- Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
- Department of Pathology, Microbiology, and Immunology, University of California, Davis, CA, USA.
- Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
- Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
- Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
- Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
- Department of Pathology, University of Georgia College of Veterinary Medicine, Athens, GA, USA.
MeSH Terms
- Animals
- Female
- Horse Diseases / diagnostic imaging
- Horse Diseases / pathology
- Horses
- Immunohistochemistry / veterinary
- Lymphocytosis / diagnostic imaging
- Lymphocytosis / pathology
- Lymphocytosis / veterinary
- Lymphoma, B-Cell / diagnostic imaging
- Lymphoma, B-Cell / pathology
- Lymphoma, B-Cell / veterinary
- Microscopy, Electron, Transmission / veterinary
- T-Lymphocytes / pathology
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