CANINE EPULIDES
Background
Greater than 40% of all oral tumors are of dental or periodontal origin. There are three types of epulides: fibromatous epulides, ossifying epulides, and acanthomatous epulides.
All arise from the periodontal ligament; therefore they are intimately related to the dental arcade. Fibromatous epulides and ossifying epulides are benign, whereas acan- thomatous epulides may act aggressively by destroying bone and surrounding tissue. Other terms that have been used to describe acanthomatous epulis include adamantinoma and ameloblastoma, although ameloblastoma may be a distinct tumor seen in young dogs. Most of these tumors are considered benign, although acanthomatous epulides can be locally aggressive.Epulides affect both sexes at equal rates. Although most affected dogs are middle-age, the age range is wide. Epulides have been documented in dogs as young as 1 year and as old as 15 years of age. Although boxers may be predisposed to developing gingival hyperplasia, this breed does not seem to be at excessive risk for developing epulides.
Clinical Parameters
Dogs with epulides often have malodorous breath, facial swelling, or a lump on the gums. Fibromat- ous and ossifying epulides are slow-growing, discrete masses that rarely exceed 2 cm in diameter. They are firm gingival tumors covered by oral epithelium.They may be single or multiple but are always discrete and located near teeth. Ossifying epulis differs from fibromatous only in osteoid production.
Acanthomatous epulis is a more rapidly progressive tumor that has a high epithelial component and infiltrates readily into bone. It is usually found in the mandible but may also occur in the maxilla.
Clinical Work-up
On first presentation, epulides may look like other oral tumors; therefore a biopsy of the tumor,aspirates or biopsies of regional lymph nodes, radiographs of the affected bone, chest radiographs, and blood work are warranted.
Fibromatous and ossifying epulides are not invasive; therefore high-detail radiographs of the affected bone are unlikely to identify changes in bone. Such radiographs may be helpful in assessing the degree of the specific bony destruction caused by acanthomatous epulides. In one series of 39 dogs with acanthomatous epulis, radiographic changes in bone were primarily osteolytic in 23 dogs and osteoblastic in only 8 dogs. More than 50% of the bone must be replaced by tumor before lysis is evident radiographically; therefore radiographs should not be relied on for surgical margins. Computed tomography (CT) may assist in delineating the margins of tumor involvement more accurately. Technetium-99m nuclide scans tend to overestimate tumor margins by imaging peripheral reactive bone.Therapeutic Approach
Local gingival excision of an epulis is unlikely to be curative for most cases.These tumors arise from the periodontal ligament and can recur from subgingival tumor tissue. Surgery can be curative if surgical margins include the affected tooth root, as with mandibulectomy or maxillectomy. If normal bone is included in a wide surgical excision, the procedure should be curative. With larger tumors, however, tumor-free margins may be difficult to obtain. In a series of 37 dogs treated with surgery for acanthomatous epulis, there was just 1 local recurrence and all dogs were alive at 1 year. Cryosurgery has been used for treatment of epulides, but it is difficult to penetrate bone using this modality and therefore recurrence is common. Cryotherapy should not be used if it will delay more definitive treatments.
Radiation therapy is a very effective treatment for acanthomatous epulis. In one report of 39 dogs that received between 20 and 70 Gy of orthovoltage radiation therapy on a Monday, Wednesday, Friday schedule, 27 of the dogs had a complete remission. The majority (30 of 39) received 35 to 50 Gy. Twelve dogs did not have a complete regression of visible tumor.
Regrowth occurred in only 3 dogs at 8, 18, and 24 months after radiation. Two of these dogs had tumors that responded to reirradiation. Overall survival ranged from 1 month to 102 months, with a median of 37 months. These dogs did not have surgery before radiation therapy. Possible adverse effects of orthovoltage radiation are osteonecrosis and malignant transformation of the original epulis at the site of radiation. Malignant transformation occurred in 7 dogs at a median of 47 months after radiation therapy. One can reasonably hypothesize that some of these tumors may have been initially misdiagnosed as epulides. In another series of 37 dogs with acanthomatous epulis, progression-free survival for 3 years was 80% after cobalt-60 radiation therapy.These dogs were treated with megavoltage radiation to a total of 48 Gy delivered over 4 weeks on an alternate- day schedule of 4-Gy fractions. Most of the tumors recurred within the field rather than at the margins. Malignant tumor formation at the site of previously irradiated acanthomatous epulides was reported as a complication in 4 of 32 dogs treated in one study.In one dog an acanthomatous epulis regrew 6 weeks after receiving 50 Gy of orthovoltage radiation therapy. This dog had almost complete regression of the tumor after 10 doses of doxorubicin (30 mg/m2 intravenously every 3 weeks) and cyclophosphamide (50 mg/m2 orally daily for 4 days every week) and had stable disease for at least 20 months after starting chemotherapy.
In one study four dogs with acanthomatous epulides were given bleomycin intralesionally. The dose given was 5 mg weekly. Tumors disappeared within 3 to 10 weeks, and no adverse effects were noted. No tumor recurrence was noted for these dogs.
When considering therapy for acanthomatous epulis, the age of the patient should be considered. In younger dogs, surgery may be offered as the treatment of choice owing to the risk, albeit low, of radiation-induced tumorigenesis. For geriatric dogs, radiation-induced malignant transformation may be less of a concern due to the protracted course of this phenomenon. Alternatively, radiation can be considered for the first course option with a reasonable probability of being successful with surgery for the second option, should radiation fail.
Ameloblastomas have been reported in young dogs. These tumors also arise from odontogenic tissue, but they are distinct from acanthomatous epulides. Two dogs younger than 1 year of age with ameloblastoma were treated with surgery; tumors recurred in both dogs within 6 months. A second surgery resulted in a cure for one of these dogs, with no recurrence 105 months after surgery.