Mandibular osteosarcoma in a goat

Introduction-A few large surveys on tumour prevalence in goats indicate that tumours in general are quite common in this species. Reviews of neoplastic diseases in goats indicate a prevalence ranging from 0,8 to 11%. However, osteogenic tumours arising from facial bones in goats are rare. Regarding oral localization only a few mesenchymal tumours have been described arising from the gengiva. Case presentation-A 4-year old, female crossbred goat was referred with a history of dysorexia and a slow growing painful mass on the face. On physical examination the animal showed poor body condition and the left side of the face was deformed by a voluminous mass which, at the inspection of the oral cavity, displaced the maxillary teeth. Differential diagnoses included os-teomyelitis and benign (osteoma, chondroma, ossifying and non ossifying fibroma, odontogenic tumours) as well as malignant (osteosarcoma, chondrosarcoma) mesenchymal tumours arising from either the connective tissue and bone. The goat was euthanized because of the extension of the lesion and a complete necropsy was performed. Grossly, the face was deformed by the presence of a hard mass arising from the branch of the left mandible. Histologically the oral mass was composed of heterogeneous proliferation of malignant osteoblasts intermigled with brightly eosinophilic strands or island of osteoid matrix. Neoplastic cells, interpreted as malignant osteoblasts, were characterized by plump to round or spindle-shape morphology, with moderate basophilic cytoplasm and an eccentrically located voluminous nucleus containing a large prominent nucleolus. Mitotic figures were found and were either bipolar and atypical. At necropsy no metastases were found and the final diagnosis was non-metastasizing mandibular osteoblastic osteosarcoma. Conclusion-In conclusion, regardless the type of tumour, the goat was euthanized because of the extension and the severity of the lesion. Necropsy and histological examination were necessary to correctly classify the tumour as a non-metastasizing mandibular osteosarcoma.