Adenomatoid odontogenic tumor is a very rare tumor that affects the upper or lower jaws. In the past 10 ten years only four such tumors were diagnosed at the College of Dentistry, King Saud University. A fifth case is presented with a review of the literature. The current case appeared to mimic a dentigerous cyst in the mandible. The management of such cases is also discussed.
 

Adenomatoid odontogenic tumor was classi- fied in many reports as a variant of ameloblas- toma, but Stafne¹ in 1948 considered it as a distinct entity. The first description of the tumor was documented in 1907 and was called as a pseudo- adenoma adamantinoma.² In 1969, Philipsen and Birn³ proposed the name adenomatoid odontogenic tumor and, due to its different behavior, suggested that it should not be regarded as a variant of ameloblastoma. Since that time, much evidence has reinforced this concept.

Our current understanding of the odontogenic adenomatoid tumor has come about through ana- lyzing the information gained from numerous case reports. Several extensive review articles dealing with the subject is available.⁴"¹⁰ A survey was compiled by Courtney et al⁴ in 1975 where twenty cases had been studied. In 1970, Giansanti and colleagues⁵ investigated 108 reported cases and added three cases to the literature.
 

A 20-year-old male Saudi university student was referred to the Oral Surgery Division to investigate a swelling in the chin region. The patient also noticed tilting in some anterior lower teeth sometime before observing the swelling. However, no pain was reported.

On examination, the patient looked healthy with an obvious swelling over the left side of the chin but no cervical lymphadenopathy [Fig. 1] was noticed. Mouth opening was normal, with no deviation on maximum opening.

Intraorally, the patient had almost full com- plement of teeth except for a missing lower left canine and a retained lower deciduous left canine. The overlying mucosa appeared normal in color and texture. A firm buccal swelling extending from the lower right central incisor to the region of the retained deciduous left lower canine could be seen [Fig. 2]. There was also lingual expansion in the lower left incisor-canine region. A tilting of the teeth, associated with swelling, could be seen with no abnormal mobility of any of them. All lower teeth reacted positively to thermal and elec- tric pulp testing. No alteration in lip sensation was recorded. An orthopantomogram revealed a large, well-circumscribed radiolucency extending throughout the anterior part of the mandible from the right to the left premolar regions [Fig. 3]. The lesion expanded, with resorption of the inferior cortex in some area, extending upward into the alveolar process disturbing the usual orientation of the lower anterior teeth. The unerupted permanent lower left canine was associated with the lesion. Differential diagnoses of the lesion included odon- togenic cyst and odontogenic tumor.

The patient's general health was excellent and examination of his systems, as well as his laboratory results, were within normal limits.

Under endotracheal anesthesia, a labial mu- coperiosteal flap, extending from the right to the left second premolar region, was raised. The buccal plate in the anterior part of the mandible was found to be very thin and, in some areas, eroded. A tumor mass was found occupying the

whole chin region [Fig. 4] and was enucleated together with the attached unerupted lower left canine [Fig. 5], The lingual plate was found to be perforated in one area.

None of the anterior teeth was attached to the tumor mass and were, therefore, left in position to be clinically followed post-operatively. The speci- men, including the canine tooth, was histologically examined. The resultant bony defect was left to fill in with the patient own blood. A Redi-Vac drain was inserted before suturing the buccal flap back into position. His post-operative recovery was uneventful and healing of the surgery site was normal.

Histopathology

Microscopic examination described multiple sections from different planes of the specimen received which were exhaustively stained with H&E and trichrome stains. Histology revealed a very interesting lesion because of the juxtaposition of the odontogenic epithelial and fibrous connec- tive tissues.

The odontogenic epithelium, which is le- sional, consisted of spindle and cuboidal or colum- nar cells without clear cell boundary. These cells were arranged in whorls, sheets, organoid and alveolar patterns, or frank ducts. In between cells, basophilic calcified amorphous masses were pre- sent. These calcific masses were also present next to, but at times outside, the adenomatoid arrange- ment of the cells [Figs. 6,7].

The other areas of the section histologically showed desmoplasia with whorling and dense col- lagenization of the connective tissues. Normal mitoses were evident. The border of the lesion was present corresponding to the attenuated buccal and lingual plates, where bone trabeculae under- gone resorption. Dysplastic bone appeared to be forming in the aggressively cellular area of the desmoplastic zones. The extensive fibromyxoid tissue configures as a very broad connective tissue capsule of partly ductal and partly cystic but predominantly solid, odontogenic epithelial lesion. Diagnosis was adenomatoid odontogenic tumor, with unusually extensive fibromyxoid connective tissue.

Clinical Course

Due to the benign nature of the tumor, a decision was made to observe and follow-up the operating site regularly at 6-month intervals. All teeth near the lesion reacted positively to vitality testing methods.
 

The adenomatoid odontogenic tumor is an uncommon histological type of odontogenic tumor which is characterized by the formation of duct- like or rosette-like structures by the epithelial component. Recent ultrastructural and enzyme - histochemical studies suggest that adenomatoid odontogenic tumor originates from the enamel organ epithelium."¹²

When compared to the simple amelo- blastoma, the odontogenic adenomatoid tumor has different clinical features and microscopic configu- ration. It is a lesion which characteristically affects the anterior part of the jaws of patients in their second decade of life.⁵ It presents as a slow- growing, painless swelling. Radiographically, the odontogenic adenomatoid tumor is seen as a uniloc- ular radiolucency that is frequently associated with an unerupted tooth. Conservative surgical excision is curative. The ameloblastoma on the other hand is most frequently noted in the posterior part of the mandible of patients in the fourth decade. Radio- graphically, ameloblastoma tends to present as a multilocular lesion rather than the dentigerous cyst- like radiolucency associated with the odontogenic adenomatoid tumor. Ameloblastoma tends to be locally invasive necessitating more radical proce- dure.

A review of the records at the College of Dentistry, King Saud University in Riyadh showed that in the past ten years only four cases of adeno- matoid odontogenic tumor were diagnosed (Table 1).

In our case, the patient was male and the affected region was the mandible. For cases in which the lesion appears to surround an unerupted tooth and has no radiopaque component, dentiger- ous cyst may also be considered in the differential diagnosis. However, the adenomatoid odontogenic tumor often appears to envelop the crown and root as in this case. Dentigerous cysts rarely encircle the root.⁵ Enucleation of those lesions should be sufficient to effect treatment. The reported recur- rence rate of adenomatoid odontogenic tumor is very low (0.2%).^8,13