T-cell lymphocytic leukaemia and lymphoma in a horse

Abstract

Extract A 10-year-old Thoroughbred gelding showed rapid weight loss over about 1 week. Clinically, it had increased respiration and heart rates, dark red mucous membranes with petechial haemorrhages, and a bilateral keratitis. Routine haematological examination showed a lymphocytosis with increased numbers of small hyperchromatic lymphocytes in circulation, but no anaemia. On necropsy, many enlarged abdominal lymph nodes were seen and there was a large amount of fluid in the peritoneal cavity and pericardial sac. Histopathologically, small lymphocytes infiltrated most tissues including the bone marrow, lymph nodes, liver, gastrointestinal tract and cornea. These were identified as T-lymphocytes by the use of immunohistochemistry and CD3 (positive), CD20 (negative) and CD 79a (negative) markers. A T-cell lymphocytic leukaemia and multicentric lymphoma with generalised tissue infiltration were therefore diagnosed.