Three Cases of Mandibular Ossifying Fibroma in Cattle.

Neoplastic masses were evaluated in the rostral region of the mandible of three young adult cattle. In all three cases, the masses were macroscopically large, firm, ulcerated, infiltrative, whitish and solid, and led to tooth displacement and loss. Radiographically, the neoplastic masses were intraosseous and radiolucent with foci of radiopacity. Loss of radiopacity due to bone necrosis was seen in the mandibular bone adjacent to the neoplasms. Histologically, well-differentiated, infiltrative non-encapsulated mesenchymal neoplastic proliferation replaced the mandibular bone and extended to the oral mucosa in all three cases. The neoplastic cells had scant cytoplasm and fusiform or oval hyperchromatic nuclei with loose chromatin, and were arranged in bundles in various directions. Within the neoplastic tissue, there were mineralized bone trabeculae and unmineralized osteoid, lined by a layer of osteoblasts and osteocytes within the lacunae. The pre-existing bone tissue adjacent to the neoplasm had areas of necrosis and osteoclasis of variable extent and intensity. Based on the macroscopic, radiographic and microscopic findings, a diagnosis of mandibular ossifying fibroma was established in all three cattle.