engleski

Osteosarcoma of the Mandible in a Geriatric Horse - a Case Report

Osteosarcoma (OS), a malignant neoplasm of bone is a rare tumor in horses. Most cases have been attributed to young horses. This report presents a case of OS of the mandible in a horse. A 21-year-old Warmblood gelding was presented with a history of weight loss, painful swelling of the left lower jaw, halitosis, quidding and reduced appetite lasting for 8 months. On presentation the horse was depressed, with BCS 3/9, bilateral temporal muscle atrophy and swelling of the left body of mandible. Intraoral examination revealed hard swelling of the left ramus mandible from 306 to 311. Radiography showed a huge expansile, aggressive bone lesion involving most of the left mandible. Osteolysis was predominant with sun-burst periosteal proliferation. Periapical area of 306 to 311 was radiolucent with total alveolar bone destruction. Mandibulectomy was rejected by the owners and the horse was euthanised. Postmortem analysis involved the head and included computed tomography (CT) scan, histopathology (HP) and immunohistochemistry (IHC). CT scan revealed a tumor mass with bone destruction and lytic lesions. The lesion extended from 306 to the caudal border of the ramus mandible. The ventral border was destroyed and replaced by connective tissue stroma. HP showed densely to loosely arranged spindle to polygonal cells that form intertwined bundles. Cells had scant to moderate eosinophilic cytoplasm and roundish or irregularly shaped nucleus. Anisokaryosis and karyomegaly were present, likewise a moderate number of giant multinuclear cells. Mitoses were 0-3/HPF. Multifocally there were islets of osteoid, bone, necrosis and purulent inflammation with bacterial colonies. IHC showed positivity for vimentin, small number of cells for cytokeratin. The diagnosis of ostoblastic and fibroblastic OS (mixed type) with epithelioid differentiation was made. This report emphasises the importance of considering OS as a differential diagnosis in cases of mandibular mass in old horses.

osteosarcoma, mandible, horse

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