Adenomatoid Odontogenic Tumor of Mandible - A Case Report.

INTRODUCTION

Adenomatoid odontogenic tumour (AOT), an uncommon benign epithelial lesion of odontogenic origin, was first d e s c r i b e d b y D r e i b a l d t i n 1 9 0 7 a s pseudoadenoameloblastoma. In 1915, Harbitz reported it as admantoma¹. In 1948 Stafne considered it a distinct entity, but it was classified others as a variant of ameloblastoma. Later, Birn proposed the name adenomatoid odontogenic tumor in 1969 and suggested that it not be regarded as a variant of ameloblastoma². In 1999 Philipsen and Reichart presented a review based on reports published until 1997 which showed some interesting aspects regarding epidemiological figures of this tumor³. In 2003 Max and Stern coined the name Adenomatoid Odontogenic Cyst⁴. Adenomatoid odontogenic tumour comprise only 0.1% of tumors and cysts of the jaw. Philipen et al. reported that they account for 3-7% of all odontogenic tumors⁵. Philipsen and Reichart have described three clinico-topographic variants of this lesion. These include: follicular variety is associated with an unerupted tooth whereas the extrafollicular variety is not associated with an impacted tooth. These follicular and extrafollicular variants constitute about 96% of all Adenomatoid odontogenic tumour of which 71% are of the follicular variety. Radiographically, in the follicular variety the radiolucency surrounds the crown and a part of the root of the impacted tooth. In the extrafollicular variant, the radiolucency may be located in between, above, or may be superimposed upon the roots of erupted permanent tooth. The peripheral (extraosseous) type is seen as a growth on the gingiva similar to a gingival fibroma or epulis characteristically attached to the labial gingiva of the tooth bearing area of the alveolus⁶. Steriolithography, technological advances in image collection, through more and more developed plans such as helicoidal computerized tomography, have allowed the creation of a prototype or model construction technology, in a reduced time, known as Rapid Prototyping (RP). It is a process of organs and objects reproduction by scanning the area to be prototyped, usually through a computerized tomography or magnetic resonance exams⁷.

CASE REPORT

A 28 years old female patient consulted to our unit with the complaint of hard swelling on right back region of the mandible with asymmetry of face since 3-4 months. The swelling was small in size a year back and now gradually increased to a present size with asymptomatic. On extraoral examination, asymmetry of the face was observed due to a hard swelling on right posterior region of the mandible (Fig.1). Altered vestibular region with normal mucosal colour, more buccal cortical plate expansion with mild lingual cortical plate expansion was observed on intraoral examination. But more significant and interesting was unerupted both the premolars was observed (Fig.2). Orthopantamograph, revealed well defined, large unilocular radiolucency extending from mesial surface of canine to distal surface of first molar anteroposteriorly and extending from lower border to the crest region with missing first premolar. Lesion was associated with impacted second premolar which was located at lower border of the mandible and observed intact inferior border. Displacement of canine with root resorption of first molar was also observed (Fig.3). Computed tomography-axial section revealed lesion measuring respectively about 3.24cms X 3.00cms, anteroposteriorly and mediolaterally. Expanded cortical plate with impacted second premolar at centre and lower border of the lesion was observed (Fig.4). After hemogram report, aspiration revealed no significant feature. Considering as a special case, we advised for Steriolithography of the mandible to collect more information, diagnosis and its treatment plan. In Steriolithography study, we revealed and are able to collect the accurate size, shape, cortical plate expansion, extension of lesion, with accurate location of the impacted tooth and also cortical plate perforation (Fig.5). With all other radiographic study and computed tomography reports, a Steriolithography provided an excellent 3D view model of the lesion of the mandible which helped us for the treatment plan. Surgical removal of lesion along with impacted premolar and also extraction of canine and first molar was performed. Followed by curettage and iliac bone grafting was performed (Fig. 6, 7, 8 and 9). Excised lesion was sent for histopathological report and revealed adenomatoid odontogenic tumour. Postoperative frontal view was taken and healing was eventful (Fig.10). Case was followed up for three years and revealed no recurrence (Fig. 11).

DISCUSSION Adenomatoid odontogenic tumour is slowly growing lesion, with a predilection for the anterior maxilla (ratio of cases 2:1 relative to mandible) of young females. Generally tumours do not exceed 1-3 cm in greater diameter, but they can be larger. The lesions are typically asymptomatic, but the growth of the types with central lesion results in cortical expansion. The involved teeth are commonly impacted, and adjacent teeth may be slightly displaced. Root resorption is a less common finding. If the lesion is large, it can cause a painless hard swelling. The origin of Adenomatoid odontogenic tumours is controversial. According to hypothesis, the lesion (sometimes while forming a cystic space) next to or into a nearby dental follicle, leading to the envelopmental theory². Compared with ameloblastoma, Adenomatoid odontogenic tumour occurs at a significantly lower age. Based on the fact of AOT being a well encapsulated tumour that expands centrifugally, i.e. equally in all directions, Adenomatoid odontogenic tumour may cause expansion of the cortical plates at an early stage compared with ameloblastomas, which spread linearly within the cancellous bone before causing expansion or resorption of the cortical plates⁸. Radiographic findings of Adenomatoid odontogenic tumour frequently resemble other odontogenic lesions such as dentigerous cysts, calcifying odontogenic cysts, calcifying odontogenic tumours, globulomaxillary cysts, ameloblastomas, odontogenic keratocysts and periapical disease. Whereas the follicular variant shows a well circumscribed unilocular radiolucency associated with crown and often part of the root of an unerupted tooth³. Recent reports indicate that cells of an adenomatoid odontogenic tumour usually differentiate toward an apparent ameloblastic phenotype but fail to achieve further functional maturation. WHO has described the histologic features of the tumour as follows, a tumour of odontogenic epithelium with duct like structures and with varying degree of inductive changes in the connective tissue. The tumour may be partly cystic and in some cases the solid lesion may be present only in the wall of a large cyst and it is generally believed that the lesion is not a neoplasm⁴. A review of literature depicts a lesion in which conservative management produces uniformly excellent outcome without recurrence⁹. First point of interest with this tumour is to make correct anatomicopathological identification and not to confuse with the other, more aggressive forms of odontogenic tumours. It is given as a benign behavior, slow growth and clear delimitation, as well as its low tendency to recur, the treatment of choice is enucleation and simple curettage, although in exceptional cases of large tumours or risk of bone fracture, partial resection enbloc of the anterior mandible or maxilla has been indicated. Additionally, the use of lyophilized in cases where  surgical extirpation has left a large exposed osseous cavity.¹⁰

As in our case after collecting the patient's history and clinical examination, we advised radiography and computed tomography to rule out further. Differential diagnosis was adenomatoid odontogenic tumour or dentigerous cyst of mandible. With consideration of present condition we advised for steriolithography for its treatment plan. Surgical excision of the lesion along with impacted second premolar was removed. Due to large and extensive involvement of the lesion, extraction of canine and first molar also removed then followed by curettage. Considering as large lesion removal with its defect, there was more prone for fracture of mandible and to avoid this iliac cancellous bone grafting was placed. In our case simple curettage with iliac cancellous bone grafting was the treatment plan to avoid pathological fracture including long term follow up.

CONCLUSION

Adenomatoid odontogenic tumour is a benign and relatively a rare lesion in the mandible. Recurrence rate is low and prognosis is good. Including radiographic and computed tomographic reports, in absence of patient a Steriolithography will provide 3D model view of the lesion which is precise and more informative for the involvement into adjacent structures with its extension. Certainly, also for the treatment plan whether we have to plan for conservative management with grafting or resection and reconstruction to avoid extraoral approach. Long term follow up is mandatory in case of conservative management of adenomatoid odontogenic tumour.