Adenomatoid Odontogenic tumor in an 8 year old patient : Report of a case

INTRODUCTION

Adenomatoid odontogenic tumor, commonly referred to as AOT is a benign odontogenic neoplasm. The behavior of this entity is, it can show aggressive nature also. The incidence rate of this lesion is 0.1% of all tumors of head and neck and within the odontogenic tumors it represents 3-7%¹ . This entitles it to be the fourth most common odontogenic tumor. The clinical variants of this tumor are follicular, extra follicular and peripheral² . It is commonly referred to as “twothirds tumor”, as 2/3 cases occur in maxilla, 2/3 cases are seen in young females and 2/3 of the cases are in association with an unerupted tooth especially canine³ . This tumor was first described by Dreibaldt in 1907 as pseudoadenoameloblastoma⁴ . It was considered as a distinct entity by Stafne and the term AOT was first accepted by WHO (World Health Organization) in the year 1971⁵ .

Case Report

An 8 year old child visited the dental office with a chief complaint of pain and swelling in the upper left back region of the jaw since one month. There was no history of associated trauma. On clinical examination the patient had diffuse swelling on the extra oral region measuring around 3 cm from the nasolabial fold in a posterior direction and around 3cm on the maxillary region extending from below the infraorbital ridge unto the upper lip. The borders of the swelling were diffuse. On palpation, the swelling was non tender, non fluctuant and bony hard in consistency. Regional lymph nodes were not enlarged. Intraoral examination revealed obliteration of the vestibule from the region of the deciduous left maxillary canine unto deciduous left maxillary molar regions. The associated teeth exhibited no carious lesions but had grade I mobility. Mucosa overlying the swelling was normal without any sinus discharge. Panaromic radiograph revealed a well defined unilocular cystic lesion ranging in size around 3X3 cm. There was resorption of the roots of deciduous teeth in the radiograph. A Cone beam computed tomographic image of the lesion was also performed which revealed a 38.6 X 30.3mm well defined unilocular corticated cystic lesion surrounding the neck of the permanent first premolar tooth [Fig. 1]. A provisional diagnosis of dentigerous cyst was rendered. A differential diagnosis of Central giant cell granuloma, Adenomatoid Odontogenic tumor and Ameloblastic fibroma was considered. The lesion was surgically explored and enucleated under general anaesthesia with mucoperiosteal flap raised from the deciduous left maxillary canine and upto the deciduous left maxillary second molar [Fig.2]. Surgical exploration revealed that the lesion showed the soft tissue attached near the neck of the unerupted/impacted maxillary first premolar which was extracted. The deciduous first and second molar which exhibited grade I mobility with resorption of roots were also extracted. The area was irrigated and closed surgically. The lesion healed properly. The patient was recalled for further check up and rehabilitation for space maintenance, for which the patient did not eventually report back. The gross specimen exhibited whitish tissue surrounding the neck of the crown of permanent first premolar [Fig. 3]. The H and E stained studied sections of the submitted tissue showed a cystic lumen with thin non keratinized epithelial lining. There was proliferation of spindle shaped cells in the form of nodules, whorls and rosette formation. Duct like proliferation along with dystrophic calcifications were also observed [Fig. 4 & 5]. Histopathological sections confirmed the diagnosis of Adenomatoid Odontogenic tumor.

Discussion

AOT is a relatively rare, hamartomatous benign epithelial lesion. Among the odontogenic cysts and tumors, the incidence of AOT is 2-7%.⁶ According to WHO, this tumor is defined as being comprised of odontogenic epithelium in an array of histoarchitectural patterns, embedded in mature connective tissue stroma and characterized by gradual but progressive growth with generally no tendency of recurrence. Our present case shows its occurrence with an impacted permanent first premolar tooth which is in contrast with the reported literature where canines are the most commonly involved teeth. More commonly it has been seen in association with canines, followed by incisors, premolars and molars⁷ .

This tumor is more commonly seen in young females, the youngest age of the patient reported was that of a hybrid tumor with AOT in a 2 year old female patient reported by Soares et al⁸ . Three variants of this tumor have been described namely intraosseous follicular, extrafollicular and peripheral variants. The intraosseous follicular variant is commonly seen in association with an impacted tooth. Our clinical case can be considered under this category as it was seen in association with impacted first premolar tooth. The second variant of this tumor is intraosseous extrafollicular one which has no association of impacted tooth. It may be seen superimposed on the roots of the teeth. The third one is the peripheral variant which is a soft tissue counterpart occurring as a gingival lesion. Regarding its histogenesis also there are two classes of thought. Few regard it as being a hamartoma and while others regard it as a neoplasm. Molecular studies by Razavi et al using ki-67 labelling index signified it to be a hamartoma⁹ while Gomes et al suggested it to be neoplastic. They used human androgen receptor gene polymorphism assay10. The suggested cells of origin for AOT are varied. These include enamel organ, reduced enamel epithelium, undifferentiated odontogenic epithelium, stratum intermedium cells and cells of dental lamina⁶

The clinical nature of this tumor is said to be indolent, but our present case showed aggressive nature with a short history of duration of 1 month. There was root resorption of the deciduous canine, first molar and second molar teeth. The general size of AOT’s do not generally exceed 1-3 cm in diameter¹¹. Our lesion measured around 30.3mm x38.6mm in size with buccal and palatal cortical plate expansion. Radiographic interpretation in our present case gives the impression of dentigerous cyst, as there was no evidence of any radioopaque calcifications within the lesion.

The histology of this tumor is unique. Typically it consists of spindle shaped cells in the form of solid nodules, nests, duct like structures, rosettes, trabeculae, cribriform pattern and in the form of sheets. Eosinophilic amorphous material is seen in between these epithelial cell nodules or within the rosette or duct like structures. There can be occasional foci of mitotic activity. The connective tissue is minimal or scanty. The histopathology findings of the lesion in our case had no correlation with the aggressive behavior as regular histopathologic findings were observed. Our sections showed spindle shaped cells arranged in the form of whorls, nodules, rossettes along with few calcifications. There was no evidence of mitotic activity. The treatment consisted of surgical enucleation. The other differential diagnosis considered in our case was that of dentigerous cyst as this is the most commonly associated lesion with an impacted tooth. The differential diagnosis of Central Giant cell Granuloma was considered owing to the aggressive behavior of the lesion. Central giant cell lesion has a tendency for occurence in young age and has aggressive potential with root resorption of the involved teeth. Thus owing to the rapid growth this was also considered to be one of the differential diagnosis, though the patient could not recollect any history of trauma. Ameloblastic fibroma, though a rare entity and anterior maxilla is an unusual site it was also considered among the differential diagnosis owing to the age group and its rapid growth. After ruling out all other possibilities and histopathologic confirmation, the diagnosis of AOT was rendered. Our present case highlights the occurrence of this tumor with a premolar tooth which is rare and also its rapid growth suggests that the AOT’s may not be more indolent. Thus emphasis should be made to include AOT in the differential diagnosis of aggressive lesions especially during the first and second decade of life.