Small intestine large granular lymphoma in a horse.

This article is detailing the diagnosis of a rare type of lymphoma identified in a 12-year-old Appaloosa gelding horse, which was only detected after its death. It underscores the unusual confinement of the disease to the small intestine, distinguishing it from similar past instances where such large granular lymphomas affected other areas.

Background of the Case

• The study came out of a case wherein a 12-year-old Appaloosa gelding horse was brought into the Texas Veterinary Medical Center. The horse had a history of chronic diarrhoea and weight loss.
• Post mortem examination of the horse revealed numerous oval, craterlike ulcers throughout the small intestine.

Diagnostic Findings

• On examination of the ulcers, histologically, they were made up of a new growth or neoplastic proliferation of round cells. These cells contained phosphotungstic acid-hematoxylin-positive granules within their cytoplasm.
• On further analysis with immunohistochemical staining, the tumor cells tested positive for the CD3 antigen, a T-cell marker, and negatively for a B-cell marker. This indicated the presence of a certain type of lymphoma in the horse’s small intestine, known as large granular lymphoma.

Unusual Presentation of the Case

• This particular case was unusual because the entire lymphoma was confined to the small intestine, without any involvement of the regional lymph nodes, a common characteristic in such cases of lymphomas.
• The morphologic and immunohistochemical characteristics of the neoplasm were typical of large granular lymphomas. However, the restriction of this neoplasm to the small intestine was atypical in comparison to previously documented cases of such equine large granular lymphomas, which usually affect other abdominal areas.

Implication of the Findings

• The finding of this case implied that large granular lymphomas can occur exclusively in the small intestine of horses, contrary to previous assumptions. This opens a new horizon for further investigations into the pathophysiology and treatment options for such localized large granular lymphomas.