Canine Maxillofacial Parosteal Osteosarcoma: A Retrospective Case Evaluation in 10 Dogs.

Parosteal osteosarcoma (OSA) is a subtype of surface OSA that is considered slow growing with a less aggressive biological behavior compared to central OSA and, therefore, carries a better prognosis with surgical excision. Parosteal OSA has a predilection for the skull in dogs with documented more frequent occurrences on the zygoma, maxilla, or coronoid process of the mandible, all of which present unique challenges to the oral surgeon. Ten cases of parosteal OSA of the canine maxillofacial bones are summarized and discussed in this report. The most common bone of origin was the caudal maxilla and/or zygoma in 50% of tumors. Exophthalmos was a prominent clinical sign noted in 40% of dogs. Median survival time was 14 months, with a one-year survival rate of 60%. Metastasis to the lungs was suspected in three cases. The histopathological diagnosis of parosteal OSA is crucially dependent on diagnostic imaging. When a primary bone tumor of the maxillofacial bones is suspected, it is essential for the oral surgeon and pathologist to collaborate to provide informed guidance on surgical planning, anticipated long-term outcomes, and clinical monitoring for these patients. The goals of this retrospective study are to identify key clinical and radiographic features, improve recognition for accurate diagnosis, and establish treatment recommendations for canine maxillofacial parosteal OSA.