A case of a dog with mandibular extraskeletal osteosarcoma after long-term puncture extirpation of the salivary gland cyst in the mandible.

Background: Extraskeletal osteosarcoma, unlike skeletal osteosarcoma, is a rare malignant mesenchymal tumor with a soft tissue primary that has been reported to occur in a variety of soft tissues.

Case Description: The case is a 14-year-old, unneutered male Miniature Pinscher, weighing 6.7 kg, who had been treated medically for more than 5 years with a management strategy of puncture extirpation of a salivary gland cyst in the mandible; 1 month earlier, the fluid retention could not be removed, and after a computerized tomography scan showed no lesion in the mandible adjacent to the mass lesion, surgical resection was performed.