Odontogenic Tumors

The actual incidence of odontogenic tumors is unknown because these lesions are often assumed (wrongly) to be incidental.  Consequently, they are frequently not biopsied.  Odontogenic tumors (OTs) arise from those embryonic tissues destined to develop into teeth and associated structures.  OTs are considered neoplasms (cancers) that range from benign to invasive in biologic behavior.

Historically, OTs have been referred to or categorized as being Epulides or an Epulis.  These terms have no specific histopathologic connotation and are clinical terms used only to describe any localized swelling on the gingiva.  Both terms are commonly used incorrectly today by many veterinarians and pathologists.  Because confusion exists, these are often mistakenly considered benign, inconsequential and not biopsied.  This may have disasterous consequences for the pet/patient.

Because many of these so called “epulides” are actually odontogenic tumors, a definitive biopsy diagnosis by a pathologist with formal training and experience in the pathology of odontogenic tumors and cysts is required.  Treatment planning should occur only after a definitive biopsy diagnosis has been established.

Some of the more common Odontogenic Tumors:

Ameloblastomas
Ameloblastomas are non-inductive, soft tissue tumors that in spite of their benign appearance, should be considered locally invasive neoplasms that do not metastasize.

Because they are usually painless, patients are usually asymptomatic in the early stages.  On X-Rays, it is common to see bone lysis with unilocular or multilocular cystic structures around tooth roots.  They are considered to be benign tumors with invasive properties into surrounding bone. The preferred treatment modality is surgical excision with appropriately wide margins.  Recurrence is common and may be disasterous.  Incomplete surgical removal, before a diagnosis is established, is the most common reason for recurrence. 

Ameloblastomas are considered rare in cats and those that do exist are sometimes confused with other more common types of ondontogenic tumors in this species.

Peripheral Odontogenic Fibroma:
Many of the gingival enlargements previously described as fibromatous and ossifying epulides have been reclassified as peripheral odontogenic fibromas (POFs).  POFs are slowly growing, benign neoplasms that are common in dogs and may be seen in cats.   Histopathology is necessary to definitively diagnosis POFs.  These tumors contain proliferative fibroblastic connective tissue, as well as, proliferative ondontogenic epithelium associated with foci of a variety of hard tissues suggesting induction.   Complete surgical excision, with appropriate margins, is usually curative.

Amyloid Producing Ondontogenic Tumor
This OT type is rare in dogs and cats and presents as a gingival swelling on either jaw in patients between 8 to 13 years of age.  These tumors are locally invasive, however, not metastatic.  On radiographs, the lesions are often cystic and may resemble an ameloblastoma.  The presence of amyloid (Congo Red stain), which tends to calcify, is a characteristic histopathological finding of this tumor.  Surgical excision, with appropriate margins, is necessary to completely remove this invasive neoplasm.

Feline Inductive Odontogenic Tumor
This tumor is unique to young cats (usually 8 to 18 months).  FIOTs are raised, submucosal soft tissue masses most commonly located on the rostral maxilla.  This tumor is considered locally invasive, however, it does not metastasize.  Complete surgical excision is required.

Odontomas
Ondontomas are benign inductive tumors diagnosed in young dogs and cats of 6 to 18 months.  Some consider odontomas as actually being malformations and not neoplasms.  These are well differentiated, non-invasive, tumors characterized by the simultaneous occurrence of soft and hard dental tissues (enamel, dentine, cementum, dental papilla).  An odontoma in which rudimentary tooth-like structures (denticles) are present is referred to as a compound odontoma.  An odontoma in which the arrangement of dental tissues is haphazard, is called a complex odontoma.

The radiological appearance is characteristic. Complex odontomas appear as opaque amorphous masses while compound odontomas appear as numerous tiny teeth in a focal area.  Complete surgical excision is usually curative.