Figure 1-A: Peripheral odontogenic fibroma arising from the gingiva of the left maxillary first incisor (tooth 201). Photo courtesy John Lewis, VMD, FAVD, Dipl. AVDC Gingiva is the specialized oral mucosa that forms a protective collar around each tooth and extends to the mucogingival line. Epulis (plural = epulides, pronounced epp-you-LID-eeze) is a term that refers to any oral mass arising from the gingiva. However, the term has become synonymous in veterinary medicine with certain tumor types. Historically we have referred to three types of epulides: fibromatous, ossifying and acanthomatous. In more recent years, the terminology has changed to steer away from the general term “epulis.” Fibromatous epulis and ossifying epulis are now grouped into the same category, “peripheral odontogenic fibromas.” This month’s column will discuss the diagnostic and treatment approach to peripheral odontogenic fibromas. Start With Biopsy In general, when presented with any oral mass, a veterinarian first should obtain an incisional biopsy because the test results may show that aggressive treatment is not warranted. A biopsy may be obtained in the form of a wedge taken with a scalpel blade, a cylinder acquired from a biopsy punch or a mass removed at its base if attached via a pedunculated stalk. Figure 1-A shows an oral mass in a 6-year-old mixed-breed dog. The mass is large and covers a large portion of the rostral hard palate. Fibrosarcoma could easily look similar in this location, so why did I suspect the mass was a peripheral odontogenic fibroma? The tumor’s attachment is a key piece of information. Fibrosarcoma is often very sessile in its attachment, presenting as a diffuse swelling. Peripheral odontogenic fibromas are often pedunculated or circumscribed. With the latter, enlargement of the gingiva often occurs circumferentially around a specific tooth and can extend to adjacent gingiva of other teeth, but adjacent mucosa is generally not involved. Figure 1-C: Radiograph of the same oral mass seen in Figure 1-A. Note the movement of tooth 201 to a more mesial position and the relative lack of root resorption. Small punctate areas of mineralization can be seen within the portion of the mass surrounding the crown of tooth 201. As seen in Figure 1, the mass surrounds and obscures viewing of the tooth from which it arose (left maxillary first incisor, tooth 201), but adjacent teeth are relatively unscathed. Take Dental Radiographs The radiographic appearance of an oral tumor helps with diagnosis. Peripheral odontogenic fibromas usually do not cause lysis of adjacent alveolar bone. The ossifying type of peripheral odontogenic fibromas may show evidence of mineralization within the mass on dental radiographs. In contrast, acanthomatous epulis—now referred to as acanthomatous ameloblastoma—results in bone invasion and bone lysis, requiring removal of a margin of clinically and radiographically normal adjacent tissue to prevent recurrence. Removing a 1-centimeter margin of normal tissue in all directions around acanthomatous ameloblastoma is a reliable rule of thumb for preventing recurrence. A peripheral odontogenic fibroma that causes hard tissue changes is usually the result of slow growth of the tumor, which led to movement of teeth and minimal root resorption (Figure 1-C). My approach to the mass that surrounded tooth 201 and extended onto the palate was based on clinical suspicion, the fact that the mass was present for a long time and evaluation of the attachment of the mass. In this case, I chose to excise the gingiva circumferentially around tooth 201, which allowed a collar of 201’s gingiva and the larger portion of the tumor to be delivered in one piece. Figure 1-B: Mass removed at the level of the mucogingival line. Tooth 201 was extracted, and a flap of alveolar mucosa was raised to close the defect. The tooth that the mass seemed to arise from was extracted, and the site was closed via a pedicle flap and two releasing incisions in the alveolar mucosa dorsal to the alveolus of tooth 201 (Figure 1-B). Patient No. 2 Figures 2-A and 2-B show another common appearance of a peripheral odontogenic fibroma associated with the buccal gingiva of the right maxillary fourth premolar (tooth 108) in a boxer. Multiple other gingival masses /gingival enlargements were seen in all quadrants. This multilobulated mass arising lateral to tooth 108 is sessile, appearing from the gingival margin of the tooth on the buccal surface but not wrapping around the tooth onto the palatal surface. Because this dog’s multiple gingival masses had never been biopsied, I opted to remove all the masses/enlargements at the level of the normal gingival height and submit samples from six sites for pathological evaluation. Biopsy results of the mass at tooth 108 returned as a peripheral odontogenic fibroma. Results from the other sites showed either peripheral odontogenic fibroma or gingival hyperplasia. Figure 2-A: Multiple gingival masses found in all four quadrants of a boxer. None of the masses had been previously biopsied. Having the results, I recommended monitoring for evidence of recurrence but did not propose further surgical treatment at that point. Figure 2-B: Masses were removed at the level of the normal gingiva and submitted for histopathology. All biopsies returned as peripheral odontogenic fibromas or gingival hyperplasia. Extraction of the tooth from which the tumor arose will prevent recurrence. However, not all peripheral odontogenic fibromas will recur when removed at the normal gingival margin, so extraction of functionally important teeth may not always be necessary. If the mass recurs, removal of the mass and associated gingiva and extraction of the tooth or teeth that it arose from should be curative. References Fiani N, Verstraete FJ, Kass PH, Cox DP. “Clinicopathologic Characterization of Odontogenic Tumors and Focal Fibrous Hyperplasia in Dogs: 152 cases (1995-2005).” J Am Vet Med Assoc. 2011;238(4):495-500. Soukup JW, Bell CM. “Nomenclature and Classification of Odontogenic Tumors—Part I: Historical Review.” J Vet Dent. 2014;31(4):228-232 Bell CM, Soukup JW. “Nomenclature and Classification of Odontogenic Tumors — Part II: Clarification of Specific Nomenclature.” J Vet Dent. 2014;31(4):234-243. Dr. John Lewis practices veterinary dentistry and oral surgery at NorthStar Vets in Robbins-ville, N.J. Columnists’ opinions do not necessarily reflect those of Veterinary Practice News. Originally published in the October 2016 issue of Veterinary Practice News. Did you enjoy this article? Then subscribe today!
