Lymphosarcoma with leukemia in a horse.

The research article discusses the diagnosis and detailed examination of a horse suffering from Lymphosarcoma with leukemia, with focus on understanding the cytologic and ultrastructural characteristics of the disease.

About the Clinical Presentation

• The horse in the study, a 17-year old Arabian gelding, exhibited symptoms of Central Nervous System (CNS) depression and weight loss.
• Physical examination revealed generalized lymphadenopathy (condition characterized by lymph nodes which are abnormal in size, number or consistency), pitting edema (a condition causing swelling, primarily in legs or arms) and ascites (accumulation of fluid in the peritoneal cavity, commonly seen in patients with liver disease).

Diagnosis and Findings

• The diagnosis of lymphosarcoma with leukemic manifestations was made on the basis of some key findings:
• Cytologic and histopathologic examination of lymph node biopsy samples: This involves examining the cells and tissues under a microscope to search for disease.
• The horse had a peripheral leukocyte count of 98,300/microliters, approximately 94% of which were mature lymphocytes. Lymphocytes are white blood cells that are an important part of the immune system. This indicated an abnormally increased count.

Analysis of the Lymphocytes

• The circulating lymphocytes lacked B-lymphocyte markers, a sign usually associated with abnormalities in the cells for immune response.
• These lymphocytes also did not respond to mitogenic stimulation, indicating functional incompetence. Mitogenic stimulation is a process to induce cell division (mitosis).
• Even though the ultrastructural findings were equivocal, most morphologic changes indicated that these cells were likely of the T-lymphocyte lineage. Ultrastructural study is a method to study cell structure under an electron microscope.
• Virus particles were not observed during transmission electron microscopy of these lymphocytes, thus ruling out viral infection in the lymphocytes as the cause of the disease.