Abstract
We studied 34 chondrosarcomas and 17 osteosarcomas among 285 sinonasal neoplasms in the dog. Mesenchymal chondrosarcomas (24) were more common than ordinary chondrosarcomas. Ultrastructural studies done in one case confirmed mesenchymal chondrosarcoma. Of the osteosarcomas, fibroblastic osteosarcoma (7) was the most common. In contrast to non-sinonasal skeletal neoplasms which are composed mostly (80%) of osteosarcomas, chondrosarcomas (66%) and mesenchymal chondrosarcomas (47%) were predominant among the sinonasal skeletal neoplasms of this study. The average age (ten years) of the dogs with sinonasal osteosarcoma was higher than that of dogs with non-sinonasal skeletal osteosarcoma, and there was a distinct male predominance in the dogs with osteosarcoma and chondrosarcoma. Large breed dogs and boxers, frequently affected with skeletal neoplasms, were not affected commonly with sinonasal osteosarcoma. The frequency of metastasis in the dogs with chondrosarcoma and osteosarcoma was much lower than that seen in dogs with nonsinonasal skeletal neoplasms.