Adenomatoid Odontogenic Tumor – AOT

Adenomatoid odontogenic tumor was formerly considered to be a variant of aneloblastoma and was called as Adenoamelobalstoma.

It is termed as AOT in short and represents 3% to 7% of all odontogenic tumors. It is considered as a Hamartoma rather than a true Neoplasm because of Slow growth and Circumscription of the lesion. AOT is classified as a mixed odontogenic neoplasm which is an Epithelial tumor with an inductive effect on the odontogenic ectomesenchyme.

Age incidence of AOT: Seen in Younger patients 10-30 years of age

Radiographic Features of AOT:

• Well circumscribed unilocular radiolucency
• Radiolucency involves the crown of an unerupted tooth
• It is similar Radiologically to Dentigerous cyst
• Radiolucency related to follicular type of Adenomatoid odontogenic tumor sometimes extends apically along the root past the cementoenamel junction, which is not seen in Dentigerous cyst a very good way to differentiate between AOT and Dentigerous cyst
• Snowflake Clacifications can be seen in AOT
• Extrafollicular type of AOT is seen below the roots of Unerupted tooth and not around an unerupted tooth

Clinical Features of AOT:

• Seen mostly in the anterior region of Jaw
• Seen twice as commonly in Maxilla as in Mandible – 2 Maxilla > Mandible
• Seen twice as commonly in Females as in Males – 2 Females > Males
• Size is mostly 3 cms in diameter
• AOT is asymptomatic and is discovered mostly of routine radiographic examination to assess the location of unerupted tooth.
• Peripheral (extraosseous) forms of the tumor are rare
• Small, sessile masses on the facial gingiva of the maxilla
• Clinically AOT cannot be differentiated from Gingival fibrous lesions
• When the lesion is bisected the central portion of AOT shows a Solid or varying degree of Cystic change

Histologic Features of AOT:

•  AOT is a well defined lesion with a thick fibrous capsule keeping the contents circumscribed
• Tumor is composed of Spindle shaped epithelial cells that form sheets, strands or whorled masses of cells in a scant fibrous stroma
• The epithelial cells may form Rossette like structures about a central space which may be empty or contain small amounts of eosinophilic material which may stain for Amyloid.
•  Tubular or Duct like structures which are the charecteristic feature of the adenomatoid odontogenic tumor may be prominent, scanty or even absent in a given lesion.
• They consist of a central space surrounded by a layer of columnar or cuboidal epithelial cells
• The Nuclei of these cells tend to be polarized away from the central space, mechanism of formation of these tubular cells is not known but is supposed to be due to the secretory activity of the tumor cells which appear to be preameloblasts
• These structures are not true ducts and no glandular elements can be seen in the tumor
• Small foci of calcification can be seen scattered throughout the tumor, which have been interepted as abortive enamel formation
• Some AOT contain larger areas of matrix material or calcification which has been interpreted as dentinoid or cementum
• In the periphery of the tumor we can see anatomosing cords of epithelium in an eosinophilic, loosely arranged matrix.

Treatment of Adematoid Odontogenic Tumor:

Eneculation is the most used and easy procedure for AOT because of the presence of a capsule which separates the tumor from the bone.