Odontogenic Oral Tumors

Information below intended for veterinarians.
Some photos may be graphic.

Update on Classification of Odontogenic Oral Tumors

Benign, locally invasive, or malignant?

How can you tell?


Non neoplastic masses such as gingival hyperplasia, infectious conditions, and tumors of odontogenic origin may be confused with malignant tumors by their appearance. Conversely, oral neoplasms may present as non-healing ulcerated lesions instead of the typical prominent oral mass.

Oral tumors often go unnoticed by owners until they are very advanced. Therefore, it is important to perform as thorough an oral exam as possible for each patient’s annual or semi-annual visit.

While malignant oral tumors represent 6% of all canine tumors (the percent is even lower in felines); the actual incidence of oral and odontogenic tumors (OT) is unknown because of confusion regarding nomenclature and the fact that many practitioners don’t routinely submit specimens for histopathology. The most detailed information regarding OT has come from human studies, which does not always apply to our companion animals.

Odontogenic tumors arise from remnants of embryonic tissues programmed to become teeth or other oral tissues. Traditionally, odontogenic tumors have been referred to as epulides (singular epulis) though in fact, an epulis may be used to describe any localized exophytic swelling on the gingiva.

Epulides have since been divided into 3 categories:

  1. Reactive lesions
  2. Odontogenic tumors or cysts
  3. Non-odontogenic tumors (usually malignant)

Thus, it is important not to consider that all epulides are benign!
All localized discrete masses on the gingiva warrant biopsy and histopathology.

Even a dog with generalized gingival hyperplasia with a localized mass should have it excised and evaluated by a pathologist (one who is well informed regarding oral tumors).

In 2002 a revision was suggested to the World Health Organization regarding previous classification of OT. This classification was approved in 2005.

While many localized gingival enlargments are reactive and may require only conservative management, ex. Gingival hyperplasia where excision of “false” periodontal pockets, diligent homecare and frequent professional periodontal treatment are sufficient.

Oral TumorPhotograph at right represents pathology that may occur as the result of gingival hyperplasia left untreated.

Other lesions, even if classified as benign may require much more aggressive treatment. For additional information on gingival hyperplasia, see Dallas Veterinary Dentistry News Jun 2011 newsletter.

For example, lesions previously classified as fibrous, acanthomatous or ossifying epulides have been reclassified and treatment recommendations have changed as well. Fibrous and ossifying epulides are now called peripheral odontogenic fibromas. Peripheral odontogenic fibromas are generally slow growing benign neoplasms and the surface epithelium may appear normal. (See photograph below right). Unfortunately, this photograph represents regrowth of the tumor that had been excised two times prior.

Oral TumorTreatment recommendations with this histopathology report warrants en bloc resection of the mass and underlying bone to prevent recurrence.

Regrowth of these tumors may result in difficulties in prehension and mastication (note how the tumor has displaced the incisors in photo at right).

Any mass removed at the gum line that has regrown requires additional more aggressive surgery, and/or referral to a board certifed veterinary dentist.

NOTE: Many pathologists are still reporting these lesions a fibrous or ossifying epulides!

Oral TumorThe most important change in classification is that of the acanthomatous epulis. (Photograph at right). The current classification: canine acanthomatous ameloblastoma (CAA) typically appears as an exophytotic gingival mass with an irregular surface. It is considered benign because it doesn’t metastasize, but is very invasive into the surrounding bone. In fact, if left untreated may infiltrate the alveolar bone and cause tooth displacement. This particular tumor had also invaded bone of the maxillary sinus.

Treatment recommendations for CAA’s because of its’ aggressive nature requires en bloc excision and excision of at least 1cm of normal tissue. In many cases, this may require a partial mandibulectomy or maxillectomy. Radiation therapy is another option with good results reported. Documented side effects of osteonecrosis or subsequent malignant transformation still leave wide surgical excision, the treatment of choice. NOTE: Many pathologists are still reporting these tumors as acanthomatous epulides.



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