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The Epulis: What’s in a Name?

By John R. Lewis, VMD
For Veterinary Practice News

Posted: Jan. 25, 2012, 6:05 p.m. EST

Practitioners and technicians in general practice are on the front line of diagnosis. Early detection of oral tumors improves outcome.

Gingival masses may result from neoplastic, hyperplastic, inflammatory or infectious causes. Any mass arising from the gingiva may be correctly referred to as an “epulis” (plural is “epulides”).

However, the term “epulis” has been adapted in veterinary nomenclature to describe specific gingival tumors arising from periodontal ligament cells, including acanthomatous, fibromatous and ossifying epulides.

In recent years, the nomenclature for these odontogenic tumors has changed. Fibromatous and ossifying epulides are now often referred to under the same heading of “peripheral odontogenic fibromas.” Based on histological appearance, acanthomatous epulis is now referred to as “canine acanthomatous ameloblastoma.”
This article describes a clinically rational approach to gingival masses noted during conscious oral examination.

1. Start with a thorough oral examination
On conscious oral examination, look for clues of whether the gingival mass is neoplastic, hyperplastic, benign or malignant. Is it well-circumscribed? Is there evidence of mobile or displaced teeth in the area?

Acanthomatous ameloblastoma
Classic appearance and location of locally invasive canine acanthomatous amelobastoma.Copyright 2011 University of Pennsylvania.
Mobile teeth are more commonly seen with malignant neoplasms due to aggressive root resorption, whereas benign neoplasms cause slow movement of teeth to a different location as the tumor enlarges. Is the surface of the tumor ulcerated, and if so, is this due to trauma from the opposing teeth, or is the tumor inherently ulcerative in all areas? Is the tumor friable, necrotic or pigmented? How do the mandibular lymph nodes feel on palpation?

2. Prepare for a thorough evaluation under general anesthesia
Though acanthomatous ameloblastoma and peripheral odontogenic fibromas have not been documented to metastasize, a more aggressive oral tumor such as squamous cell carcinoma or amelanotic melanoma may mimic their appearance.

Therefore, preoperative three-view chest radiographs are a reasonable consideration, depending on clinical appearance and size of the gingival mass. Once the patient is placed under general anesthesia, a complete oral examination is done to evaluate for evidence of other masses, including evaluation of the periodontal structures, labial and buccal mucosa, tongue, palate and tonsils.

The size and exact location of the gingival mass is recorded on a dental chart.

3. Use dental radiography to assess the extent of the gingival mass
Dental radiography is invaluable in determining the extent of disease, and is a perfect modality for imaging most small gingival masses. Larger masses, especially those arising from the caudal mandible or anywhere on the maxilla, may benefit from a CT scan, since they can often be the tip of the iceberg.

The radiographic appearance of peripheral odontogenic fibromas causes little or no loss of alveolar bone. The ossifying version may show evidence of mineralization within the center of the soft tissue swelling. Canine acanthomatous ameloblastoma typically results in some degree of bony lysis.

4. Take a biopsy to obtain a diagnosis
If a gingival mass is small and appears to be easily removed, an excisional approach may be appropriate by removing the tumor and a small margin of normal tissue. If the gingival mass shows aggressive characteristics on dental radiography, it may be wise to start with an incisional biopsy to obtain more information before proceeding with definitive treatment, because tumor type may affect treatment options and attempted margins.

Radiograph of oral tumor
Dental radiograph showing bone lysis and missing incisors in the area of the tumor.
The first tenet in obtaining a diagnosis with an incisional biopsy is to avoid seeding tumor cells into areas that might not be removed by the subsequent excisional surgery.

It is important to provide the pathologist with a helpful piece of tissue. This means avoiding inflamed and infected areas if possible. Take enough tissue to ensure a diagnosis, and send the samples to a pathologist who is familiar with oral oncology.

If multiple gingival masses are present, label each sample appropriately and write the exact location and appearance of each mass in the dental chart to avoid confusion when the histopathology results return from the lab.

5. Provide definitive treatment options based on biopsy results
Peripheral odontogenic fibromas arise from periodontal ligament cells, and therefore definitive treatment may require removal of the tooth/teeth of origin, either via a small en bloc resection or by extraction of involved teeth followed by thorough curettage of the alveolar sockets.

Acanthomatous ameloblastoma requires a more aggressive surgical approach to prevent recurrence. Although the ideal recommended margin of normal tissue to remove around this tumor type has not been definitively determined, we’ve had success with using a minimum of 1 cm margins beyond the clinical and radiographic extent of the tumor.

The most common location of acanthomatous ameloblastoma appears to be the gingiva of the mandibular incisors or mandibular canine tooth area, and rostral mandibulectomy is well tolerated in dogs.

The second most common location is gingiva of the mandibular first molar tooth. When tumors in this location are detected early, a marginal mandibulectomy1, which spares the ventral cortex and prevents mandibular drift, may be possible. When performing this technique, enough ventral, lateral and medial cortex should be spared to minimize the likelihood of future mandibular fracture. Therefore, this technique should be limited to small, dorsally located masses.

What if owners choose not to have a mandibulectomy or maxillectomy performed as curative treatment? Radiation therapy offers excellent long-term control for treatment of canine acanthomatous ameloblastoma, but malignant tumors may develop in the irradiated area in 3.5 to 12.5 percent of dogs.2,3

Intralesional chemotherapy has been reported to be successful for treatment of canine acanthomatous ameloblastoma, though side effects such as long-term bone exposure do occur, and multiple injections are generally necessary.4

6. Follow up with frequent oral examinations
Monitor patients for signs of recurrence, as well as for any new oral masses that may develop in the same site or elsewhere.

The gratifying thing about treating odontogenic gingival masses is this: Because these tumors have not been documented to metastasize, effective treatment of the primary tumor should provide a cure. Identification of these tumors in their early stages will minimize the effects of treatment on long-term function and esthetics. 

Dr. John Lewis, FAVD, Dipl. AVDC, is assistant professor of dentistry and oral surgery at Ryan Veterinary Hospital at the University of Pennsylvania.

FOOTNOTES
1. Walker KS, Reiter AM, Lewis JR. Marginal mandibulectomy in the dog. Journal of Veterinary Dentistry 2009;26(3):194-8.
2. McEntee MC, Page RL, Théon A, Erb HN, Thrall DE. Malignant tumor formation in dogs previously irradiated for acanthomatous epulis. Veterinary Radiology and Ultrasound 2004;45(4):357-61.
3.Thrall DE, Goldschmidt MH, Biery DN. Malignant tumor formation at the site of previously irradiated acanthomatous epulides in four dogs. Journal of the American Veterinary Medical Association 1981;178(2):127-32.
4. Kelly JM, Belding BA, Schaefer AK. Acanthomatous ameloblastoma in dogs treated with intralesional bleomycin. Veterinary and Comparative Oncology 2010;8(2):81-6.

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