Adenomatoid Odontogenic Tumor – A Case Report

INTRODUCTION

The Adeonomatoid odontogenic tumor which also referred to as “two thirds tumor” is a benign, non-neoplastic entity showing a slow and progressive growth. Even though numerous cases have been reported, this tumor is still considered to be ofless common.¹ The Adenomatoid odontogenic tumour had been known since many years where Nakayama had first reported two cases of AOT based on both clinical and pathologic characteristics in the year 1903 and made contribution to one of the earliest case.^2,3 A variety of terminologies had been used to describe this lesion because photomicrographic documentation was not available in that era.³ The tumor was considered as an histologic variant of the solid multicystic ameloblastoma and hence the term adenoameloblastoma was the most commonly used term for many years.² Philipsen and Birn, in the year 1969 had beenproved that the AOTs are distinguishable from SMA based on their review of 76 cases and then they proposed the term adenomatoid odontogenic tumor which was accepted and adopted by the World Health Organization in 1971.²

CASE PRESENTATION

A 18 year old female patient visited the Department of Oral and Maxillofacial Pathology with the complain of swelling in her upper left anterior tooth region present since 1 year. There was no significant medical history reported in association with the lesion. But the patient gave a history of undergoing extraction of upper front tooth 3 years back as it was erupting in an abnormal position. Extra-orally on examination, no facial asymmetry noted (Fig A). On examination, Intra-orally a diffuse swelling noted at the left upper vestibule region with respect to mesial aspect of 11 extending till the distal aspect of 24 with clinically missing 21 and 23(Fig B).

The lesion was approximately 1.5cm × 1.5cm in its greatest dimension with no secondary changes. On palpation the lesion was hard in consistency and non tender. Followed which Patient was adviced to get the radiograph of the upper anterior teeth where x-ray revealed a well defined radiolucency ofapproximately 1 cm ×1cm and impacted canine was noted(Fig C). Later on incisional biopsy (Fig D) was performed which on Histopathological examination ofH & E stained sections showed fibrous capsule with multisized solid nodules and cystic spaces interspersed with spindle cell and round to polygonal cells(Fig E). The tumor cells were exhibiting diverse morphological arrangement forming whorled, rosette and ductal pattern (Fig F). The tumor nodules composed of cuboidal or columnar epithelial cells. Eosinophilic amorphous material “tumor droplets” were noted between epithelial cells. Several areas were showing duct like spaces lined by single layer of low columnar cells with polarized nuclei away from the basement membrane and also at areas globular masses of calcified substance (Fig G) were also noticed which was suggesting of Adenomatoid odonogenic tumor.

DISCUSSION

Adenomatoid odontogenic tumor, a rare tumor accounts for 2 to 7 % of all odontogenic tumors.4,8 Among the odontogenic tumors, this tumor is the fourth most frequently occuring tumor. The occurrence of AOT is more among females compared to males with the ration of 1.9:1.2 The mean age of occurrence is approximately 18 years and can also be seen between 5-53 years.1The site of occurrence is greater in anterior maxilla than in the mandible. It isalso referred to as the two-thirds tumor since about two-thirds of tumor occurring in maxilla, two-thirds of the cases seen occured in young women (teenage years), two-thirds are usually seen in association with an impaction of canine tooth.⁴ Since the tumor associated with unerupted teeth irregular root resorption is seldom reported.⁵ Adenomatoid odontogenic tumor may occur centrally within the bones or peripheral on the gingiva.¹ The AOT produces an clinical swelling and are generally asymptomatic or sometimes noticed on a radiographic finding, or it may be discovered by rapid clinical expansion causing alarm and pain.^1,4 Some tumors can even reach large sizes (10 cm) and causing facial asymmetry.⁴ Riechart proposed three variants of AOT based on radiographic appearances.¹ Central - AOT in association with an unerupted crown (follicular).² The extrafollicular (or extracoronal) type - AOT has in no relation to the crown of an erupted or impactedtooth.³ The peripheral type - tumor is attached to the labial or the palatal gingiva.² Histologically, the tumor is surrounded by a fibrous capsule of variable thickness. The tumor composed of a spindle, cuboidal, and columnar cells exhibiting a variety of patterns⁶ like cystic, solid and scattered duct-like structures.The most striking pattern commonly encountered at low magnification is of multisized solid tumor nodules within a minimal stromal connective tissue. The tumor nodules usually exhibits cuboidal or columnar epithelial cells arranged in a nests or rosette like structures with a central area containing eosinophilic material which is oftenly called as tumor droplets.² Between the cell-rich nodules the stellate reticulum like spindle cells, and occasionally round or polygonal epithelial cells dominate the tissue. Small amounts of eosinophilic material or calcifications also may be present between these cells.1 The adenomatoid odontogenic tumoralso shows a characteristic feature of tubular or ductlike structures consisting of a central lumen which is surrounded by a layer of columnar/ cuboidal epithelial cells and nuclei of these cells are placed away from the lumen. Occasionally small scattered foci of calcifications may also bepresent throughout the tumor.⁷ Rick and Philipsen et al. have stressed that the AOT may demonstrate one or more associated cystic cavities microscopically.³ Rick has stated thatthe lining of some of these cysts may show non-keratinized, stratified and squamous epithelium which is similar to that of the lining seen in dentigerous cysts, whereas others may be lined by a less structured membrane demonstrate budlike extensions into the supporting stroma.⁷ Rick has observed and stated that a considerable number of AOTs demonstrates an identifiable cystic component, it was not clear whether these cystic component represents pooling of the mucoid stroma due to the rupture of thin latticework patternor if the tumor actually developed within or adjacent to a preexisting cyst— presumably either could occur.⁶ As all the variants of AOT shows an benign biological behaviour and since almost all are encapsulated, conservative management of the lesion like surgical enucleation or curettage is the preferred treatment of choice with few rare recurrence.⁸ In conclusion, based on the similarities of the biologic profile of AOT between our case and previous literature, we would like to conclude that though the incidence of AOT is low, it should always be inconsideration with the differential diagnosis when a case of radiolucent jaw swellings associated with an impacted permanent canine is noticed.