Linfoma de células T multicêntrico em um equino quarto de milha

Background: Equine lymphoma is the most common haematopoietic neoplasm in horses which can present a variety of clinical signs and course. The incidence of this neoplasia is of 0.7-3.2/100,000 horses. The major clinical manifestations depend on the degree of the organ involvement, the specifi c organs involved in an individual patient and duration of the disease. In general, the most common signs are weight loss, cachexia, ventral and limb subcutaneous edema, regional lymphadenopathy, depression, lethargy and recurrent fever. The purpose of the current study is to report a single case of equine lymphoma, classify this case via morphology and immunophenotyping according to the veterinary adaptation of the WHO guidelines. Case: A 19-year-old, female quarter horse showed clinical sings characterized by anorexia, weight loss, dyspnea, noisy breathing at rest, swelling in the cervical and ventral region and subcutaneous nodules. The veterinarian suspected of neoplasia. Hematological and biochemical tests were requested by the owner. The animal was euthanized due to worsening of symptoms. Macroscopically, was observed an increase of the pre-scapular and pre-crural lymph nodes and nodules in the left scapular, on the inner thigh and perineum region. On the ventral surface of the spleen was increased size of lymph nodes which showed a reddish white color. In the kidney, was observed lymph node enlargement, partially involving the subcapsular region, and hilar renal artery. In the thoracic cavity, multiple whitish nodules were found in the heart, in transition from the right ventricle to the pulmonary artery. The lung showed the enlarged mediastinal lymph nodes. In the ventral region of the trachea was observed multilobulated mass involving the thyroid region until the eighth tracheal ring, causing stenosis. The histopathological fi ndings observed in the lymph nodes were characterized by dense infi ltration of cells of small to medium size with round shape to oval, hyperchromatic nucleus and scanty cytoplasm. Among the neoplastic cells occasionally observed atypical cells, multinucleated format sometimes polyhedral with abundant eosinophilic cytoplasm, being surrounded by bands of fi brous connective tissue scarce. In the heart and trachea were found the same cell morphology. The blood test revealed mild neutrophilia and moderate leukocytosis with normal concentration of lymphocytes, however, with abnormal morphology. Immunohistochemistry revealed groups of lymphocytes with few marking weak to CD79α and strong labeling for CD3. Discussion: In the present study the lymphoma was clinically classifi ed as multicentric type because of the involvement of lymph nodes and thoracic organs. The respiratory clinical signs reported are often viewed in mediastinal lymphomas, being considered an unusual fi nding in horses with multicentric lymphoma. Differences in the histopathological classifi cation of lymphomas are reported in horses, and recently developed a classifi cation adapted for veterinary medicine based on the World Health Organization (WHO). The equine lymphoma of the present case was classifi ed as T-cell lymphoma. Due to the manifestation of lymphoma in horses occur in most cases insidiously and not showed pathognomonic clinical signs, this neoplasm should be considered in the differential diagnosis of respiratory problems in horses.