Multilobular Osteochondrosarcoma of the Vertical Ramus of the Mandible in a Cat.

A 7-year-old castrated male domestic shorthair cat presented with locked jaw syndrome and firm swelling in the right temporal region of the skull. A computed tomography (CT) scan showed a heavily calcified mass of the right coronoid process of the mandible with a popcorn appearance, consistent with a multilobular osteochondrosarcoma. The zygomatic arch was displaced laterally and ventrally due to the mass effect. The temporomandibular joint was not involved. Surgical treatment was performed and consisted of the removal of the zygomatic arch and the vertical ramus of the mandible. It was possible to open the mouth normally immediately after surgery. Recovery was uneventful. Histological examination of the mass confirmed multilobular osteochondrosarcoma. This type of tumor is rarely encountered in dogs, and a literature search reveals only 2 cases in cats: 1 arising from the skull and 1 from thoracic wall. This case report documents the first description of a multilobular osteochondrosarcoma of the mandible in a cat.