Linfossarcoma de células B multicêntrico em uma ovelha
Acta Scientiae Veterinariae
Linfossarcoma de células B multicêntrico em uma ovelha
Autor Correspondente: Luiz Francisco Irigoyen | [email protected]
Palavras-chave: diseases of sheep, lymphosarcoma, immunohistochemistry, b lymphocytes
Resumos Cadastrados
Resumo Inglês:
Background: Lymphosarcoma is a malignant tumor from tumoral cells similar to lymphocytes and its spontaneous development
in small ruminants is unusual in Brazil. In cattle, the lymphosarcomas are often associated with infection by bovine leukemia
virus (BLV), although sheep are considered as a very susceptible specie to BLV. Spontaneously lymphosarcoma is rare and in
most cases it is observed in apparently healthy animals in slaughterhouses. There is no report of this tumor in sheep in southern
Brazil. We describe a case of spontaneous multicentric B-cells lymphosarcoma in an ewe.
Case: In June 2007, a 4-years-old mixed breed ewe was necropsied after clinical signs as anorexia, weight loss and death in few
weeks. This ewe was purchased in September 2006 with another 44 sheep, most females of the same age. Dairy cattle were also
raised together with sheep at the same farm. Fragments of liver, lung, spleen, kidneys, brain and parotid lymph node were sent
to the Veterinary Pathology Laboratory - Universidade Federal de Santa Maria, Brazil, for histopathological evaluation.
Multiply white to yellow nodules, with 0.5 to 2 cm of diameter, were observed in the liver, kidneys, and the parotid lymph
node. The nodules were soft and some coalesced and infiltrating the hepatic parenchyma. The kidneys nodules were similar to
those of the liver but prominent in the capsule. They were observed infiltrating more intensely the cortical region. The parotid
lymph node was 6 x 4 x 3.5 cm size, whitish, multilobulated and the cut surface was totally obliterated by the tumor mass.
Histologically, the neoplasm showed intense proliferation of neoplastic lymphoid cells arranged in sheets and a poor
fibrovascular stroma, with round small and hyperchromatic nuclei, and scarce eosinophilic cytoplasm compressing the adjacent
parenchyma. Immunohistochemistrily, neoplastic cells were strongly positive for anti-CD79a antibody and negative for anti-
CD3 antibody, indicating neoplastic cells derived from B lymphocytes.
Discussion: The diagnostic of multicentric B-cell lymphosarcoma was made based on gross, histological, and
immunohistochemical findings. Spontaneous development of this tumor is uncommon in sheep in Brazil. The multicentric
presentation seen in this case is the most common form of lymphosarcoma in sheep, although the thymic and cutaneous forms
also occur. Sheep affected by multicentric lymphosarcomas may have symmetrical lymphadenopathy, not observed in this
case, and involvement of various organs including liver, kidney, spleen, intestine, skeletal muscle and heart. However, under
experimental conditions, these tumors are easily induced after inoculation of bovine retrovirus (BLV) in sheep, by its high
sensitivity. Possibly, the spontaneous transmission of BLV from cattle developing the disease in sheep may occur in Brazil as
well as in other countries. Epidemiological factors of the disease are not established yet. Despite this, some correlation must
exist for the low occurrence of this disease in sheep in properties of southern Brazil, where cattle and sheep are commonly
raised together, and the frequency of lymphosarcoma in sheep is low. In this case, the association of BLV with development of
the neoplasm could not be confirmed. This is the first report of multicentric B-cell lymphosarcoma in sheep diagnosed in
southern Brazil.
