Radical Tumor Resection (Maxillectomy, Mandibulectomy)

Prevalence

In dogs, peripheral odontogenic fibroma (firbromatous and ossifying epulides), acanthomatous ameloblastoma, malignant melanoma, squamous cell carcinoma and fibrosarcoma are most commonly diagnosed in the mouth. In cats, the predominant oral tumors are squamous cell carcinoma and fibrosarcoma.

Staging, Diagnosis, and Patient Preparation

The TNM system provides a method of describing the clinical extent of the malignancy. The tumor (T) is evaluated for its type, size and bone invasion. Evaluation of regional lymphatic metastasis (N) includes palpation and biopsy of the mandibular, parotid, retropharyngeal, and cervical lymph nodes. Evidence of distant metastasis (M) to the thorax, abdomen or brain is taken into account. Tumor biopsy allows establishing a diagnosis, formulating a treatment plan and providing a prognosis. Imaging gives information regarding the invasiveness of the tumor and whether surgical margins are likely to be achieved or not. Blood type determination and cross-matching are important preoperative considerations for procedures that are likely to result in significant hemorrhage. Coagulation profiles and/or buccal mucosa bleeding time may be warranted in some cases.

Maxillectomy

The relatively small size of the head and the shorter and tighter upper lip make maxillectomy far more challenging in the cat than the dog. Incisions made with a cold scalpel must be at least 1 cm away from gross or radiographically visible margins of the tumor. An additional tooth or two on either side of the desired area of excision should be extracted so that the resected area can be ‘tapered’ at each end. The mucosa is reflected with a periosteal elevator to expose the underlying bone. Hemorrhage at palatal incisions can be controlled by digital pressure and gauze sponges until the resected tissue is lifted out. Bones are channeled along the excision lines under saline irrigation with a dental bur on a high-speed handpiece or sagittal/oscillating bone saw. Osteotome and mallet may also be helpful. A large dental or periosteal elevator is inserted into cutting lines and rotated to break any remaining bony attachments. If the line of excision includes the infraorbital canal, the infraorbital artery must be identified and ligated once the specimen is elevated and lifted out. Remaining attachments are separated, and the section is removed en bloc. Traumatized turbinates are cut with scissors to leave a clean edge. Hemorrhage that cannot be controlled by ligation or pressure may respond to surface application of phenylephrine (0.05 mg/ml) given at a maximum dose of 0.1 to 0.2 ml/kg in dogs or 0.05 to 0.1 ml/kg in cats. Absorbable gelatin sponges, thrombin in a gelatin matrix, and microporous polysaccharide beads may also be useful. The defect between the nasal and oral cavities is covered with a buccal flap that is undermined until sufficient tissue can cover the defect without tension. The tissues are apposed with simple interrupted (or interspersed simple interrupted and vertical mattress) synthetic absorbable sutures. Maxillectomy in most circumstances causes minor facial asymmetry such as a palpable or visible concavity on the side of the face. If the resection includes both incisive bones and rostral portions of the maxilla, the snout will droop due to loss of the ventral support for the nasal cartilages and nasal plane. [...]