Clinical, laboratory, and histopathologic features of equine lymphoma.
Authors: Meyer J, Delay J, Bienzle D
Journal: Veterinary pathology
Summary
# Clinical, Laboratory, and Histopathologic Features of Equine Lymphoma Meyer and colleagues examined 37 horses with lymphoma (median age 5 years, range 0.3–20.5 years) to characterise the clinical presentation, laboratory findings, and cellular origin of the disease. Weight loss and ventral oedema were the predominant clinical signs, whilst laboratory profiles consistently revealed hyperfibrinogenemia (70%), hypoalbuminemia (51%), anaemia (51%), and leukemia (38%), with hyperglobulinemia and thrombocytopenia each occurring in approximately one-third of cases. Immunophenotyping and immunohistochemical staining classified 26 tumours as T-cell lymphomas and 7 as B-cell lymphomas (with 4 unclassifiable), notably revealing that five of the B-cell cases were actually T-cell-rich B-cell lymphomas infiltrated by numerous small T lymphocytes; histologically, extensive necrosis was present in 59% of cases and most tumours displayed marked architectural effacement with heterogeneous cell morphology. The finding that T-cell lymphoma predominates in horses—and the frequent presence of significant inflammatory infiltrates and necrosis—suggests that cytokine-mediated inflammation may be a key pathophysiologic feature, potentially influencing both disease progression and therapeutic response. For practitioners, these results highlight the value of immunophenotyping in confirming lymphoma diagnosis and determining lineage, whilst the high prevalence of hypoalbuminemia and systemic inflammatory markers should prompt nutritional assessment and monitoring of tumour burden in affected animals.
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Practical Takeaways
- •Weight loss and lower limb edema in horses warrant investigation for lymphoma; expect concurrent laboratory changes including high fibrinogen and low albumin
- •T-cell lymphoma dominates in equine cases, which may influence treatment planning and prognosis discussions with owners
- •Most equine lymphomas are multi-organ at presentation with significant tissue necrosis, suggesting aggressive biological behaviour and typically poor long-term prognosis
Key Findings
- •Weight loss and ventral edema were the most common clinical signs in 37 horses with lymphoma (n=25 and n=21 respectively)
- •Hyperfibrinogenemia, hypoalbuminemia, and anemia were the most frequent laboratory abnormalities (n=26, 19, and 19)
- •T-cell lymphoma was more common than B-cell lymphoma (n=26 vs n=7), with 5 of 7 B-cell tumors classified as T-cell-rich B-cell lymphoma
- •34 of 37 tumors involved multiple lymphoid tissues and abdominal/thoracic organs, with extensive necrosis present in 22 tumors