Adenomatoid Odontogenic Tumor: Clinical features, Radiology and Histopathology
Adenomatoid odontogenic tumor (AOT) is a benign tumor of odontogenic origin, that is thought to arise from the remnants of the dental lamina. It represents around 2.2% – 7.1% of all odontogenic tumors and is believed to be the 4th most common odontogenic tumor. This lesion was formerly thought to be a variant of solid/multicystic ameloblastoma and was called as “adenoameloblastoma”. Although, classified as a benign odontogenic tumor, some pathologists consider AOT to be a hamartoma, citing its limited size and lack of recurrence as a reason. However, some investigators have reported AOTs of considerable sizes and attribute the limited size of the lesion to its early detection and removal. Most AOTs (69%) occur in the second decade of life with 53% of the lesions occurring within 13-19 years of age. There is a general female predilection with at least 64% of the tumors occurring in females compared to 36% in males. Its frequency in maxilla is twice that of mandible and has a predilection for the maxillary anteriors. It is reported that 75% or 2/3rds of the cases are associated with an unerupted canine. AOT is also known to be more commonly associated with the maxillary canine than its mandibular counterpart. Most cases of AOT are diagnosed either during a routine radiographic examination or when radiographs are taken to determine the cause for a tooth’s non-eruption. They are usually asymptomatic and vary between 1 -3 cm in size. However, large lesions have been reported and may cause swelling of the jaws and facial asymmetry. A peripheral/soft tissue variant of AOT has also been reported and usually occurs as a small, sessile growth on the gingiva, more commonly on the maxilla than on the mandible. Radiographically, AOTs are of two types – the follicular and the extra-follicular type. The follicular type mimics dentigerous cyst and manifests as a unilocular radiolucency associated with the crown. However, unlike the dentigerous cyst, the
radiolucency often extends beyond the CEJ and also involves the root of the tooth. The extra-follicular variant is usually a unilocular radiolucency that is associated with an erupted tooth. The radiolucency may be in close association with the apex of the tooth root, superimposed on the tooth root, may be present between the roots of the adjacent teeth or rarely may be not in association with any teeth. Two-thirds of the radiolucencies, both follicular and extra-follicular types may have radiopaque flecs of calcified tissue. The lesion may cause expansion of cortical plates and displacement of adjacent teeth. Under the microscope, AOT shows sheets, strands or whorled masses and nodules of spindle shaped, cuboidal or columnar cells, with very little connective tissue. In the midst of these cells, characteristic
duct like as well as rosette like structures are present. These duct like structures are not true ducts and are composed of low columnar cells with nuclei polarized away from the lumen. The cells surround a lumen which may or may not possess eosinophilic material. The duct like structure sometimes possesses a rim of eosiniphilic material just above the cells and around the lumen and is called as a hyaline ring. There may be droplets of eosinophilic material in the midst of the sheets and nodules of cells and they are called tumor droplets. Also scattered throughout the lesion are foci of calcified material. There have been reports of AOT showing focal areas similar to calcifying epithelial odontogenic tumor. AOT is a benign tumor and can be treated by a conservative surgical excision and does not mandate aggressive surgery. AOT is not aggressive and seldom shows any recurrence.
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