This 7 year old Golden Retreiver presented for facial swelling and a fractured right maxillary fourth premolar. Evaluate the following images and provide your diagnosis.

The most likely diagnosis is neoplasia. Loss of trabecular detail, diffuse change in bone density, and root resorption of the right maxillary second molar is seen on the two radiographs of the right maxilla. A comparison radiograph of the left caudal maxilla is included.

The diagnosis in this patient was fibrosarcoma.