Osteoblastic Nasal Osteosarcoma in a Wagyu Bovine

Background : Osteosarcoma is a malignant mesenchymal tumor with a wide variety of histological patterns. It is the primary bone neoplasia diagnosed in most domestic animal clinic, but rare in farm animals. The tumor develops both the appendicular skeleton as the axial skeleton, the latter being less affected. Generally it has a fast, painful and infiltrative grow, being observed metastasis. This study aims to report a case of metastatic osteoblastic osteosarcoma in the nasal bone of a bovine, diagnosed at the Animal Pathology Laboratory at the University of Passo Fundo (UPF), featuring its pathological and immunohistochemical aspects. Case : A 5 year old Wagyu female beef cattle, was treated at the Veterinary Hospital of the University of Passo Fundo. The animal had swelling in the left nasal plan, dyspnoea and anorexia. It was held cytology and biopsy which revealed malignant mesenchymal neoplasm compatible with osteosarcoma. The clinical picture has worsened and the animal died. At necropsy, the left nasal plane, had ulcerated tumor mass measuring 15x12.5x7.5 cm, hard and firm consistency with whitish color that seeped up to the turbinates and sinuses. In the lung, there were numerous nodules of tumor appearance, adhered to the parietal pleura, similar to bone tissue. In the histopathological analysis, proliferation of neoplastic cells located in the deep dermis was observed, cell thick, well-defined and infiltrative, arranged in bundles, loosely grouped with rounded shape, sometimes oval, with distinct boundaries. There were areas with formation of osteoid matrix calcification and tumor necrosis. It was observed lung and regional lymph nodes metastasis. Tissue samples were subjected to immunohistochemistry (IHC), was performed using the polymer method with horseradish peroxidase (HRP), with positive control, using a panel of antibodies. Neoplastic cells were immunoreactive for vimentin and negative for other antibodies. Thus, confirmed the case of mesenchymal origin and bone tumor. Discussion : Osteosarcoma developing in the axial skeleton, more precisely in the nasal bone, in animals of this age group, is not found frequently in the literature. However, when they occur, they have unilateral injury, remarkable facial deformities, dyspnea and infiltration of adjacent tissues. During necropsy there was observed a mass of hard consistency suggesting bone tissue in the nasal plane, there was also observed whitish spots on the lung and lymph nodes. Through microscopic analysis was obtained the classification of osteoblastic osteosarcoma. Being a malignant tumor it has a fast and infiltrative growth, there was visualized metastasis in lung and mediastinal lymph nodes. The samples submitted to immunohistochemistry were positive for vimentin and negative for other antibodies. No treatment with chemotherapy, radiation therapy or surgical intervention to remove the tumor was possible to be performed. Due to the severity of the clinical condition, the mass location, which couldn’t be obtained a safe surgical margin and it was financially unviable. The presumptive diagnosis of osteosarcoma was based on clinical history, anamnesis and cytological examination. However, the histopathological examination was essential to confirm the diagnosis. Through immunohistochemical examination, it was found the histogenesis, allowing to exclude other neoplasias. This technic was essential to characterize osteosarcoma due to the shortage reports of this neoplasia in farm animals, therefore, very important in veterinary medicine diagnosis. Keywords: neoplasia, bone, axial skeleton, ruminant, immunohistochemical and anatomopathological aspects.