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Adenomatoid odontogenic tumor

Adenomatoid odontogenic tumor (AOT) was formerly termed adenoameloblastoma because it was believed to be a subtype of ameloblastoma that contains ductlike or glandlike structures. Clinically, microscopically, and behaviorally, it is clearly different from ameloblastoma, and the term adenoameloblastoma is not used.

Adenomatoid odontogenic tumor surrounding the crown of an impacted tooth.

Clinical and radiographic features

Adenomatoid odontogenic tumour is uncommon, completely benign and a hamartoma not a neoplasm. Its name comes from its histological resemblance to a gland because it contains duct-like structures. Three variants of this tumour have been identified: follicular (73% of cases), extrafollicular (24%), and peripheral (3%). AOT is rarely seen in association with other benign odontogenic tumors and cysts.

Adenomatoid odontogenic tumours present in late adolescence or young adulthood are more common in females than males.

 Most develop in the anterior maxilla and form a very slow-growing swelling resembling a dentigerous or radicular cyst or are chance findings in the follicle of an extracted unerupted tooth/ impacted teeth.

Radiographically, the follicular AOT is a well-circumscribed unilocular lesion that usually appears around the crown of an impacted tooth; the extrafollicular type  presents as a well-defined unilocular radiolucency above, between, or superimposed over the roots of an unerupted tooth.

 Lesions typically are radiolucent but may have small opaque foci distributed throughout, reflecting the presence of calcifications in the tumor tissue.

When they are located between anterior teeth, divergence of roots may be seen. The peripheral type is characterized by a painless, nontender gingival swelling.

When in the wall of a cyst, a subtle radiographic clue is fine speckled mineralisation around the wall.

Adenomatoid odontogenic tumour: key features

  • Rare
  • Hamartoma of odontogenic epithelium
  • Usually presents between ages 15 and 30 years
  • Most common in the anterior maxilla
  • Often appears radiographically as a dentigerous cyst
  • Encapsulated – treated by enucleation

A panoramic view shows an adenomatoid odontogenic tumor occurring as a unilocular radiolucent lesion surrounding the crown of the right maxillary impacted permanent canine.

A calcifying epithelial odontogenic tumor is seen in the left posterior mandible as a mixed lesion with dense opaque foci associated with an impacted tooth.

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