Lymphoma, Equine
Basic Information 
Epidemiology
Genetics and Breed Predisposition
Genetic causes may exist because rare reports exist of aborted feti affected by lymphoma.
Clinical Presentation
Disease Forms/Subtypes
• Generalized: Regional lymph nodes are often affected with involvement of the thoracic and abdominal organs. Solitary tumors in various tissues also occur but less commonly. Clinical signs and diagnostic findings depend on the affected tissues. Chronic disease with often acute, severe terminal progression of clinical signs. Most commonly affects horses 5 to 10 years of age, but all ages are at risk.
• Alimentary: Most common in young horses ages 2 to 5 years. Presenting complaints include weight loss, ill thrift, intermittent colic, fever, and chronic diarrhea. Diagnosis can be made by cytologic analysis of peritoneal fluid in 35% to 50% of cases.
• Mediastinal: May cause dyspnea, cough, recurrent pleural effusion. Most commonly affects horses 5 to 10 years of age.
• Cutaneous: Generalized cutaneous or subcutaneous nodules with acute or chronic onset or progression. Lesions may be affected by hormone alterations (eg, pregnancy, estrous).
Diagnosis 
Differential Diagnosis
• Generalized form: Chronic systemic infections, such as internal abscessation or bacterial pneumonia; other forms of metastatic neoplasia (adenocarcinoma, carcinoma)
• Alimentary form: Gastrointestinal parasites, inflammatory bowel disease, chronic bacterial enterocolitis
• Mediastinal form: Bacterial pneumonia or pulmonary abscessation, pleuropneumonia, metastasis of other forms of neoplasia (adenocarcinoma, carcinoma)
• Cutaneous form: Folliculitis, furunculosis, dermatophytosis, nodular necrobiosis, urticaria, amyloidosis
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