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15 April 2020 - Case of the Month #490

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Case of the Month #490

Clinical history:
A 17 year old girl presented with a 2 cm maxillary lesion surrounding an impacted canine tooth.

Histopathology images:


What is your diagnosis?

Click here for diagnosis, test question and discussion:



Diagnosis: Adenomatoid odontogenic tumor (AOT)

Test question (answer at the end):
Which of the following scenarios represents the most common set of clinical features associated with the follicular variant of adenomatoid odontogenic tumor (AOT)?

A. Posterior mandible, unerupted first molar tooth, middle age female
B. Anterior mandible, unerupted central incisor tooth, elderly male
C. Anterior maxilla, unerupted canine tooth, teenage female
D. Posterior maxilla, unerupted premolar tooth, teenage male



Discussion:
Adenomatoid odontogenic tumor (AOT) is an uncommon, benign and clinically well circumscribed odontogenic tumor representing 2 - 7% of all odontogenic tumors (Neville: Oral and Maxillofacial Pathology, 4th Edition, 2015). The term ‘‘adenomatoid odontogenic tumor’’ was proposed by Philipsen and Birn (Acta Pathol Microbiol Scand 1969;75:375) in 1969 and adopted by the World Health Organization in 1971. The histogenetic source of the tumor cells remains uncertain and possibilities include the enamel organ epithelium, reduced enamel epithelium, rests of Malassez and remnants of dental lamina associated with the gubernacular cord (Head Neck Pathol 2011;5:123). AOT has a strong predilection for individuals in their first three decades of life, with nearly 90% of cases occurring in the second and third decade. Females are affected about twice as often as males.

AOT is known to exhibit three clinicopathologic variants: intraosseous follicular (pericoronal) which is most common, intraosseous extrafollicular (extracoronal) and peripheral (extraosseous). The follicular type appears radiographically associated with the crown and often with part of the root of an unerupted tooth, whereas the extrafollicular type is not associated with unerupted teeth. The peripheral variant is associated with gingival tissues (J Oral Pathol Med 1992;21:348). AOT is commonly asymptomatic and may be discovered during the course of a routine radiographic examination taken to determine why a tooth has not erupted in the expected anatomic location. It has a striking predilection for the anterior region of the jaws and is found twice as often in the maxilla as in the mandible (Dentomaxillofac Radiol 2012;41:533).

The histological findings in AOT are similar regardless of the clinicopathologic presentation. The tumor is circumscribed and surrounded by a fibrous capsule (Mod Pathol 2019;32:799). The tumor is composed of spindle shaped cells arranged in whorled nodules with juxtanodular spindle cells present in either patternless arrays or concentric layers. Rosette-like structures are present. Eosinophilic amorphous material (tumor droplets or eosinophilic coagulum) is present between spindled cells and in the center of the rosette-like configurations. The whorled nodules of spindled cells may be connected by anastomosing strands of basaloid epithelial cells in a plexiform, reticulated or lattice work pattern.

Columnar or cuboidal epithelium forms duct-like spaces set within the spindled, whorled nodules with nuclei which are displaced away from the apparent lumen. The duct-like spaces, from which the tumor gets its name, may be prominent, scant or in some cases inconspicuous. Small, punctate foci of calcification are scattered throughout the tumor. Some AOT contain larger areas of calcified matrix material, including Leisegang type calcifications, dentinoid or cementum.

The differential diagnosis of AOT includes dentigerous cyst, ameloblastoma, calcifying epithelial odontogenic tumor and dentinogenic ghost cell tumor.

AOT is treated by enucleation. Recurrence after enucleation seldom occurs, which justifies conservative management (J Oral Pathol Med 2019;48:10).

Test question answer:
C.
Anterior maxilla, unerupted canine tooth, teenage female
AOT in general has a strong predilection for individuals in their first three decades of life, with nearly 90% of cases occurring in the second and third decade. Females are affected about twice as often as males. AOT is commonly asymptomatic and may be discovered during the course of a routine radiographic examination taken to determine why a tooth has not erupted in the expected anatomic location. It has a striking predilection for the anterior region of the jaws and is found twice as often in the maxilla as in the mandible. The follicular type appears radiographically associated with the crown and often with part of the root of an unerupted tooth.