There are various tissues within the oral cavity of animals that may undergo carcinogenesis (i.e., tumor formation) and eventually form tumors. Oral tumors are the 4th most common cancer formed in the dog. Tissues capable of forming tumors include, but are not limited to, the gums (figure 1), bone, tooth root, salivary tissue, cheek, palate, and even tongue. While some oral tumors are benign, the most common malignant oral tumors in the dog are malignant melanoma, squamous cell carcinoma (SCC), and fibrosarcoma. Surgical excision is often the first and most definitive step in treatment. The most common malignant oral tumors in the cat are SCC and fibrosarcoma.
Some of these tumors can be treated with surgery that only require soft tissue removal, while others may require that part of the upper jaw bone (maxilla) or lower jaw bone (mandible) be removed. Dogs tend to handle extensive oral surgery well, and even within hours of removing part of the jaw via maxillectomy (upper jaw) or mandibulectomy (lower jaw), most dogs will be ready to eat. Cats, however, commonly have reduced or no desire to eat after oral surgery, so a temporary feeding tube, which will allow you to feed and administer medications to your cat through a simple tube in the neck, is often recommended until the cat is healed. Unfortunately, not all cats return to normal eating following oral surgery.
- Increased salivation and/or sanguinous (i.e., bloody) oral discharge
- Facial swelling
- Weight loss
- Difficulty in prehending food
- Dropping food from mouth
- Visible mass
- Loose teeth (especially in those with otherwise good dentition) (particularly in cats)
The process of diagnosing oral tumors may begin with a simple physical examination and evaluation of the oral cavity, for which some animals may require sedation for an adequate exam. By taking your pet to their primary care veterinarian for annual examinations and routine dentals, some of these tumors may be found at an early stage before clinical signs are present. For diagnosing the type of oral cancer present, cytology obtained by using a fine needle aspirate and/or incisional biopsy for histopathologic analysis may be pursued.
Oral tumors may or may not be invasive into the bone, so radiography of the head or more advanced imaging, such as a CT scan or MRI, would be a next step recommended prior to proceeding with surgical intervention. Imaging helps ensure that the surgery has the best chance to be successful the first time.
- Mandibulectomy (taking part or all of the bottom jaw) — this list does not include all variations of mandibulectomy.
- Rostral (unilateral or bilateral) – this is taking one or both aspect(s) of the lower edge of the jaw (figure 2).
- Segmental – this is often not even noticed from the exterior of the patient.
- Complete – while dogs will still be able to eat and drink normally most of the time, there is a cosmetic change to the patient. If unilateral, mandibular drift / malocclusion and TMJ arthritis could be a high risk.
- Mandibular rim excision – this is not always appropriate for obtaining margins in removal of caudal mandibular masses (figure 3), but if it works for a patient, there is minimal change in the appearance after surgery (figure 4)
- Maxillectomy (taking part of the upper jaw) — this list does not include all variations of maxillectomy.
- Rostral (unilateral or bilateral) – if far enough back, oronasal fistula could be a risk.
- Segmental – this is often barely noticed from the exterior of the patient (figure 5).
- Hemimaxillectomy – this may occasionally be combined with removal of other structures, such as the nasal planum, entire nose, orbital bone, zygomatic arch, etc (figure 6 & 7).
- Hard palate resection
- May be performed in combination with a maxillectomy
- Feeding tube may be necessary after this surgery for a few weeks
- Partial, subtotal, near-total (75% removal of tongue)
- If more than 50% of the tongue is removed, feeding tube is necessary for at least a few weeks.
- Total – amputation of the entire tongue
- Not recommended in cats due to permanent functional complications (i.e., inability to eat, drink, or groom).
- Feeding tube is necessary for at least a few weeks for these procedures in dogs.
After part of the jaw has been removed, dogs and most cats will acclimate well to eating but will likely have a cosmetic change in their facial structure/appearance. Bilateral rostral mandibulectomy is the surgery with the biggest cosmetic change because of mandibular shortening causing excessive drooling and the tongue hanging out. Unilateral rostral and caudal maxillectomies may result in the lip being pulled toward the midline of the face and creating an indented appearance. Bilateral rostral maxillectomy often results in a drooping of the nose, since the underlying support by the maxilla is gone. Finally, the most challenging cosmetic change is with the radical maxillectomy, which shortens the upper jaw to the point of removing their nose. The dog likely does not have a change in behavior or appetite, but they may have a harder time eating and tend to be messy eaters after this procedure.
For dogs undergoing glossectomy (i.e., tongue removal), particularly subtotal, near-total, and total glossectomy procedures, heat stress / stroke is a greater risk in the future for these patients. This is due to the removal of a thermoregulation mechanism associated with the tongue of the dog, which can be addressed by avoiding hot environments and by quickly cooling the dog after activity. Drooling is another common side effect, and severity tends to be linked to how much of the tongue must be removed to address the tumor.
Minor complications, such as part of the suture line opening, are common and usually do not require another surgery. Preventing your dog or cat from rubbing their face on furniture or carpet during the first 2-3 weeks of the healing process will help to reduce the risk of complications. Your veterinarian or surgeon will give you specifics on how to care for your pet post-operatively, but an Elizabethan collar is almost always required for the first 2-3 weeks to reduce the risk of scratching of or otherwise traumatizing the surgical site.
Depending on the type of cancer removed, rechecks with your veterinarian every 3-4 months for the first 2 years is important to monitor for regrowth or local recurrence at an early stage before potentially becoming non-resectable. Referral to a medical oncologist for adjunctive therapy is often the next step, especially for the highly metastatic oral tumors, such as melanoma and SCC.
Overall, dogs will be able to return to normal life with playing, chewing on toys, and eating kibble after they heal. Cats have the potential to return to their normal behavior and appetite, but this has been shown to depend on the individual, amount of jaw (mandible vs maxilla) resected, and type of cancer. Most cats will need to keep their feeding tube in for a minimum of a few weeks until healing is complete before knowing how they will adjust longterm.