Tumors of the Lower Jaw (Mandible) in Dogs
Mandible Tumors and Growths
Tumors and growths in pets are confronted with fear and uncertainty for most pet owners. In our past article “Growths, Masses, Lumps + Tumors in Pets,” we focused on what causes them and what you can do when you find them. In this article we focus on the lower jaw or “mandible” tumors in dogs and what are some warnings signs you might want to watch-out for.
Tumors of the mandible are fairly common in middle-aged to older dogs. Often they are noticed as a fleshy swelling on the gums adjacent to the teeth. Tumors in the back of the mouth are more difficult to see and may become extensive before they are found. Occasionally owners will notice a foul odor from the mouth. Pet owners should get their pet accustomed to opening their mouth at an early age, both to examine their teeth and to inspect their mouth.
Types of Tumors
Tumors of the mandible can be either benign or malignant. Even benign mandible tumors can be locally aggressive and may require removal of some bone in order to ensure they don’t recur. The most common benign tumor is an epulis, which arises from the periodontal ligament, i.e., the ligament that attaches the tooth to the socket. There are different forms of an epulis, but most are cured with local surgery. One closely related tumor, the acanthomatous ameloblastoma, is more
aggressive and may be treated with more aggressive surgery or radiation. Malignant tumors (cancerous), which are very destructive locally, can also metastasize, or spread
to adjacent lymph nodes or other organs such as the lungs. The most common are melanomas, squamous cell carcinomas, and fibrosarcomas. Control of these tumors can be difficult, and may involve surgery, radiation, chemotherapy, or in the case of melanoma possibly a vaccine. Melanomas are especially malignant and tend to metastasize very quickly. Other types of tumors can be present, but the aforementioned ones are most common.
Diagnosis and Planning
The most accurate and efficient means of diagnosis is a biopsy. Tumors are devoid of nerves and removing a small piece for histopathology is usually a minor
procedure with simple sedation of the patient. It is often more helpful to perform general anesthesia and obtain a CT scan at the same time as a biopsy. This will determine extent of disease and aid in surgical planning. Thoracic radiographs and evaluation of regional lymph nodes are an important part of the work-up. The histopathology result will determine the type of tumor, whether it is benign or malignant, its grade (aggressiveness) and help in determining prognosis. This information, in conjunction with the CT, will help to develop an appropriate treatment plan.
Surgery is often the first line of treatment for mandibular tumors. Aggressiveness of surgery is determined by the type of tumor. Removal of part of the mandible is common, even for benign tumors. The goal of surgery is to obtain a margin of normal tissue around the tumor in an effort to prevent its recurrence. The potential for cure is very high with most benign tumors and certain malignant tumors, e.g., a verrucous squamous cell carcinoma. Lower grade malignancies tend to be slightly less aggressive and have a better prognosis than high grade tumors. As a general rule, up to 50% of the entire mandible may be removed, preserving good function and cosmetic results. The figure shows
different levels of surgical excision. Dogs return to function very quickly and most will begin eating normally within 1-2 days. Soft, formed foods, such as meatballs, pieces of chicken, or sections of hot dogs, should be given for the first 2-3 weeks. Hard toys, rawhides, and bones should be withheld during this time. Most dogs will be able to eat dry food within a few weeks. Rarely, a temporary feeding tube may be placed if a patient is experiencing a difficult time eating.
Some patients with high grade and aggressive tumors may require additional treatment e.g., radiation, chemotherapy, or vaccine.
Prognosis depends on the type of tumor, its grade, presence of metastatic disease, and completeness of excision. A surgical and medical oncologist, working together, are valuable sources for clients and patients experiencing such tumors.