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Adenomatoid odontogenic tumor (AOT) is a rare neoplasm (hamartoma) accounting for less than 3% of all odontogenic tumors. It is benign and slow-growing and is believed to originate from the remnants of the dental lamina or enamel organ. It was first described by Dreibladt, in 1907, as a pseudoadenoameloblastoma (9). In 1969, Philipsen et al proposed the name adenomatoid odontogenic tumor, which was later adopted by the World Health Organization with the understanding that this lesion has a benign and non-aggressive behavior (10). It presents within bone (intra-osseous) in 97.2% of cases and on the gingiva (extra-osseous, also known as peripheral) in 2.8% of cases (11). The intra-osseous type is further divided into follicular (most commonly) and extra-follicular types (11). The follicular type accounts for 73% of all AOT cases and is associated with the crown of an unerupted/impacted tooth, sharing the same radiographic features as a dentigerous cyst (9-12). It is a unilocular, corticated radiolucency around the crown and at times goes beyond the crown to involve the root of the tooth. The second type constitutes about 24% of cases, presenting between teeth, apical or away from teeth, and is known as extra-follicular (10-11). This type presents as a unilocular corticated radiolucency often mistaken for an odontogenic keratocyst, or lateral periodontal, residual or periapical cysts. This case would be classified as follicular in type. The peripheral variant presents on the gingival, mimicking a reactive gingival swelling. Anterior maxilla and mandible are the most common locations for AOT; cases in the maxilla outnumber those in the mandible by a ratio of two to one, and the maxillary canines in particular account for 40% of the cases. It has also been described in the posterior mandible and maxilla, but less commonly (9, 11). It is rarely described in deciduous teeth. It is more common in females (2:1 female-to-male ratio) between the ages of 10-19, with almost 70% of cases occurring in the second decade. Sizes are usually small, around 1-3 cm in diameter; occasionally, however, large lesions are described (9-10). Radiographically, it is usually unilocular and radiolucent with clearly defined to corticated margins (10-12). About 10% demonstrate some degree of calcification. AOT is usually an asymptomatic lesion with the exception of mild expansion. The extra-follicular type may cause mild displacement of teeth. Root resorption is rarely described. Histologically, it is made up of epithelial cells arranged in two patterns: some are spindle-shaped, arranged in whorls, nests and bundles, and others are cuboidal and arranged in duct-like structures. This lesion is supported a by thick fibrous connective tissue capsule. Sometimes globules of a homogenous material are described, which may represent amyloid. The treatment of choice is conservative removal through simple curettage or enucleation. The thick connective tissue capsule makes separation of the lesion from the tooth and surrounding connective tissue easy, allowing the clinician to save the tooth. Recurrence has been described but is exceedingly rare (10-12).
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