Ameloblastoma

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Large ameloblastoma adjacent to the left lower canine tooth of a dog[1]
Ameloblastoma in another old dog requiring a rim mandibulectomy[2]

Acanthomatous ameloblastoma (ameloblastic fibro-odontoma) are the second most common benign oral tumor of the canine oropharynx which results in dental disease.

These tumors are a mucosal form of basal cell carcinoma.

Commonly referred to as a form of epulis, ameloblastoma relates to the cell type of origin, odontogenic epithelial cells, and acanthomatous refers to the spiny shape of epithelial cells within these tumors[3].

These tumors usually invade the local bone of the mandible and are commonly located in the rostral aspect of the lower jaw in medium and large breed dogs[4].

Affected dogs usually present for reasons of dysphagia, bleeding gums or the condition is noticed during routine clinical examination. Radiographic or CT examination usually shows bone lysis.

Diagnosis often requires biopsy sampling and histological analysis.

A differential diagnosis would include squamous cell carcinoma (most prevalent), fibroma and fibrous hyperplasia (rostral maxilla)[5], dentigerous cyst, bone cysts, peripheral giant cell granulomas and melanoma.

They can be distinguished from oral squamous cell carcinoma based on histology and lack of expression of cytokeratins[6] and calretinin[7].

Treatment involves surgical extirpation of the lesion or rim mandibulectomy[8]. In highly invasive cases, local radiation therapy[9] or chemotherapy[10] is indicated.

Bleomycin is the drug of choice, with weekly or bimonthly intralesional injections at 10 - 20 U/m2[11].

References

  1. My Pet Dentist
  2. Veterinary Dentistry
  3. Head KW et al (2002) Tumors of the alimentary tract. In: Meuten DJ, ed. Tumors in Domestic Animals, 4th ed. Ames: Iowa State Univ Pr. pp:401–481
  4. Schmidt A et al (2012) Computed tomographic characteristics of canine acanthomatous ameloblastoma - a retrospective study in 52 dogs. Tierarztl Prax Ausg K Kleintiere Heimtiere 40(3):155-160
  5. Fiani N et al (2011) Clinicopathologic characterization of odontogenic tumors and focal fibrous hyperplasia in dogs: 152 cases (1995-2005). J Am Vet Med Assoc 238(4):495-500
  6. Arzi B et al (2011) Expression of cytokeratins in the epithelium of canine odontogenic tumours. J Comp Pathol 145(4):345-351
  7. Fulton A et al (2012) The expression of calretinin and cytokeratins in canine acanthomatous ameloblastoma and oral squamous cell carcinoma. Vet Comp Oncol Sep 18
  8. Murray RL et al (2010) The use of rim excision as a treatment for canine acanthomatous ameloblastoma. J Am Anim Hosp Assoc 46(2):91-96
  9. Mayer MN & Anthony JM (2007) Radiation therapy for oral tumors: canine acanthomatous ameloblastoma. Can Vet J 48(1):99-101
  10. Gardner DG (2012) Ameloblastomas have already been treated successfully with intralesional chemotherapy in dogs, why not in humans? Oral Oncol 48(2):e1
  11. Kelly JM et al (2010) Acanthomatous ameloblastoma in dogs treated with intralesional bleomycin. Vet Comp Oncol 8(2):81-86
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