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

Abstract

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.

Conclusion: Previous reports of extraskeletal osteosarcoma from the salivary glands in dogs have been rare. However, treatment of a salivary gland cyst in the mandible by long-term puncture extirpation may be a potential predisposing factor for the development of extraskeletal osteosarcoma around the mandible.

Keywords: Dogs; Extraosseous osteosarcoma; Mandible; Salivary gland.

Fig. 1.. External appearance of case 1 at the initial examination. A large mass (130 × 98 × 75 mm; arrow) was found in the mandible.

Fig. 2.. X-ray examination of the skull. Calcification was seen inside the mass lesion that increased from the mandible to the neck (arrow). (a) AP, anterior-posterior view and (b) LR, right lateral view.

Fig. 3.. CT scan on day 8. A hyper-absorptive area as large as the cortical bone was observed lining the entire mass wall (arrow). In the arterial phase, the interior of the highly absorbable area was occupied by a slightly less absorbable area compared to the margins of the mass lesion.

Fig. 4.. Histopathological examination results of the resected mass lesion. In the tumor tissue corresponding to the mass wall, bundles, sheets, and wreaths of osteoblast-like tumor cells (arrow) with bone formation were observed. The tumor cells were moderately atypical, and numerous mitotic figures were observed; bar, 100 μm.